The impact of detention on the health of asylum seekers: An updated systematic review: A systematic review.

Background: The number of people fleeing persecution and regional conflicts is rising. Western countries have applied increasingly stringent measures to discourage those seeking asylum from entering their country, amongst them, to confine asylum seekers in detention facilities. Clinicians have expressed concerns over the mental health impact of detention on asylum seekers, a population already burdened with trauma, advocating against such practices. Objectives: The main objective of this review is to assess evidence about the effects of detention on the mental and physical health and social functioning of asylum seekers. Search methods: Relevant literature was identified through electronic searches of bibliographic databases, internet search engines, hand searching of core journals and citation tracking of included studies and relevant reviews. Searches were performed up to November 2023. Selection criteria: Studies comparing detained asylum-seekers with non-detained asylum seekers were included. Qualitative approaches were excluded. Data collection and analysis: Of 22,226 potential studies, 14 met the inclusion criteria. These studies, from 4 countries, involving a total of 13 asylum-seeker populations. Six studies were used in the data synthesis, all of which reported only mental health outcomes. Eight studies had a critical risk of bias. Meta-analyses, inverse variance weighted using random effects statistical models, were conducted on post-traumatic stress disorder (PTSD), depression, and anxiety. Main results: A total of 27,797 asylum seekers were analysed. Four studies provided data while the detained asylum seekers were still detained, and two studies after release. All outcomes are reported such that a positive effect size favours better outcomes for the non-detained asylum seekers. The weighted average SMD while detained is 0.45 [95% CI 0.19, 0.71] for PTSD and after release 0.91 [95% CI 0.24, 1.57]; for anxiety 0.42 [95% CI 0.18, 0.66] and for depression 0.68 [95% CI 0.10, 1.26] both while detained. Based on single-study data, the SMD was 0.60 [95% CI 0.02, 1.17] for depression and 0.76 [95% CI 0.17, 1.34] for anxiety, both after release. Three studies (one study each) reported outcomes related to psychological distress, self-harm and social well being. Psychological distress favoured the detained but was not significant; whereas both effect sizes on self-harm and social wellbeing indicated highly negative impacts of detention; in particular, the impact on self-harm was extremely high. The OR of self-harm was reported separately for asylum seekers detained in three types of detention: Manus Island, Nauru and onshore detention. The ORs were in the range 12.18 to 74.44; all were significant. Authors' conclusions: Despite similar post-migration adversities amongst comparison groups, findings suggest an independent adverse impact of detention on asylum seekers' mental health, with the magnitude of the effect sizes lying in an important clinical range. These effects persisted beyond release into the community. While based on limited evidence, this review supports concerns regarding the detrimental impact of detention on the mental health of already traumatised asylum seekers. Further research is warranted to comprehensively explore these effects. Detention of asylum seekers, already grappling with significant trauma, appears to exacerbate mental health challenges. Policymakers and practitioners should consider these findings in shaping immigration and asylum policies, with a focus on minimising harm to vulnerable populations.

Participation in organised sport to improve and prevent adverse developmental trajectories of at-risk youth: A systematic review.

Background: Healthy after-school activities such as participation in organised sport have been shown to serve as important resources for reducing school failure and other problem/high-risk behaviour. It remains to be established to what extent organised sport participation has positive impacts on young people in unstable life circumstances. Objectives: What are the effects of organised sport on risk behaviour, personal, emotional and social skills of young people, who either have experienced or are at-risk of experiencing an adverse outcome? Search Methods: The database searches were carried out in March 2023 and other sources were searched in May 2023. We searched to identify both published and unpublished literature. Selection Criteria: The intervention was participation in leisure time organised sport. Young people between 6 and 18 years of age, who either have experienced or are at-risk of experiencing an adverse outcome were eligible. Primary outcomes were problem/high-risk behaviour and a secondary outcomes social and emotional outcomes. Studies that used a control group were eligible for. Studies that utilised qualitative approaches were not. Data Collection and Analysis: The number of potentially relevant studies was 43,716. Thirteen studies met the inclusion criteria. Only seven studies could be used in the data synthesis. Five studies were judged to have a critical risk of bias and were excluded from the meta-analysis. One study did not report data that enabled the calculation of effect sizes and standard errors. Meta-analyses were conducted on each conceptual outcome separately. All analyses were inverse variance weighted using random effects statistical models. Main Results: Two studies were from Canada, one from Australia, and the remaining from the USA. The timespan of the interventions was 23 years, from 1995 to 2018. The median number of participants analysed was 316, and the median number of controls was 452. A number of primary outcomes were reported but each in a single study only. Concerning secondary outcomes, two studies reported the effect on overall psychosocial adjustment at post-intervention. The standardised mean difference was 0.70 (95% CI 0.28-1.11). There was a small amount of heterogeneity. Three studies reported on depressive symptoms at 0-3 years follow-up. The standardised mean difference was 0.02 (95% CI -0.01 to 0.06). There was no heterogeneity between the three studies. In addition, a number of other secondary outcomes were reported each in a single study only. Authors' Conclusions: There were too few studies included in the meta-analyses in order for us to draw any conclusion. The dominance of Northern America clearly limiting the generalisability of the findings. The majority of the studies were not considered to be of overall high quality and the process of excluding studies with critical risk of bias from the meta-analysis applied in this review left us with only 7 of a total of 13 possible studies to synthesise. Further, because too few studies reported results on the same type of outcome, at most three studies could be combined in a particular meta-analysis and no meta-analysis could be performed on any of the primary outcomes.

PROTOCOL: Participation in organised sport to improve and prevent adverse developmental trajectories of at-risk youth: A systematic review.

This is the protocol for a Campbell systematic review. The main objective of this review is to answer the research question: What are the effects of organised sport on risk behaviour, personal, emotional and social skills of young people, who either have experienced or is at-risk of experiencing an adverse outcome? Further, the review will attempt to answer if the effects differ between participants characteristics such as gender, age and risk indicator or between types of sport (e.g., team/individual, contact/non-contact, intensity and duration).

PROTOCOL: The FRIENDS preventive programme for reducing anxiety symptoms in children and adolescents: A systematic review.

This is the protocol for a Campbell systematic review. The objectives are as follows. The main objective of this review is to answer the following research question: What are the effects of the FRIENDS preventive programme on anxiety symptoms in children and adolescents? Further, the review will attempt to answer if the effects differ between participant age groups, participant socio-economic status, type of prevention (universal, selective or indicated), type of provider (lay or mental health provider), country of implementation (Australia or other countries) and implementation issues in relation to the booster sessions and parent sessions (implemented, partly implemented or not at all).

The effects of small class sizes on students' academic achievement, socioemotional development and well-being in special education: A systematic review.

Background: Class size reductions in general education are some of the most researched educational interventions in social science, yet researchers have not reached any final conclusions regarding their effects. While research on the relationship between general education class size and student achievement is plentiful, research on class size in special education is scarce, even though class size issues must be considered particularly important to students with special educational needs. These students compose a highly diverse group in terms of diagnoses, functional levels, and support needs, but they share a common need for special educational accommodations, which often entails additional instructional support in smaller units than what is normally provided in general education. At this point, there is however a lack of clarity as to the effects of special education class sizes on student academic achievement and socioemotional development. Inevitably, such lack of clarity is an obstacle for special educators and policymakers trying to make informed decisions. This highlights the policy relevance of the current systematic review, in which we sought to examine the effects of small class sizes in special education on the academic achievement, socioemotional development, and well-being of children with special educational needs. Objectives: The objective of this systematic review was to uncover and synthesise data from studies to assess the impact of small class sizes on the academic achievement, socioemotional development, and well-being of students with special educational needs. We also aimed to investigate the extent to which the effects differed among subgroups of students. Finally, we planned to perform a qualitative exploration of the experiences of children, teachers, and parents with class size issues in special education. Search Methods: Relevant studies were identified through electronic searches in bibliographic databases, searches in grey literature resources, searches using Internet search engines, hand-searches of specific targeted journals, and citation-tracking. The following bibliographic databases were searched in April 2021: ERIC (EBSCO-host), Academic Search Premier (EBSCO-host), EconLit (EBSCO-host), APA PsycINFO (EBSCO-host), SocINDEX (EBSCO-host), International Bibliography of the Social Sciences (ProQuest), Sociological Abstracts (ProQuest), and Web of Science (Clarivate, Science Citation Index Expanded & Social Sciences Citation Index). EBSCO OPEN Dissertations was also searched in April 2021, while the remaining searches for grey literature, hand-searches in key journals, and citation-tracking took place between January and May 2022. Selection Criteria: The intervention in this review was a small special education class size. Eligible quantitative study designs were studies that used a well-defined control or comparison group, that is, studies where there was a comparison between students in smaller classes and students in larger classes. Children with special educational needs in grades K-12 (or the equivalent in European countries) in special education were eligible. In addition to exploring the effects of small class sizes in special education from a quantitative perspective, we aimed to gain insight into the lived experiences of children, teachers, and parents with class size issues in special education contexts, as they are presented in the qualitative research literature. The review therefore also included all types of empirical qualitative studies that collected primary data and provided descriptions of main methodological issues such as selection of informants, data collection procedures, and type of data analysis. Eligible qualitative study designs included but were not limited to studies using ethnographic observation or field work formats, or qualitative interview techniques applied to individual or focus group conversations. Data Collection and Analysis: The literature search yielded a total of 26,141 records which were screened for eligibility based on title and abstract. From these, 262 potentially relevant records were retrieved and screened in full text, resulting in seven studies being included: three quantitative and five qualitative studies (one study contained both eligible quantitative and qualitative data). Two of the quantitative studies could not be used in the data synthesis as they were judged to have a critical risk of bias and, in accordance with the protocol, were excluded from the meta-analysis on the basis that they would be more likely to mislead than inform. The third quantitative study did not provide enough information enabling us to calculate an effect size and standard error. Meta-analysis was therefore not possible. Following quality appraisal of the qualitative studies, three qualitative studies were judged to be of sufficient methodological quality. It was not possible to perform a qualitative thematic synthesis since in two of these studies, findings particular to special education class size were scarce. Therefore, only descriptive data extraction could be performed. Main Results: Despite the comprehensive searches, the present review only included seven studies published between 1926 and 2020. Two studies were purely quantitative (Forness, 1985; Metzner, 1926) and from the U.S. Four studies used qualitative methodology (Gottlieb, 1997; Huang, 2020; Keith, 1993; Prunty, 2012) and were from the US (2), China (1), and Ireland (1). One study, MAGI Educational Services (1995), contained both eligible quantitative and qualitative data and was from the U.S. Authors' Conclusions: The major finding of the present review was that there were virtually no contemporary quantitative studies exploring the effects of small class sizes in special education, thus making it impossible to perform a meta-analysis. More research is therefore thoroughly needed. Findings from the summary of included qualitative studies reflected that to the special education students and staff members participating in these studies, smaller class sizes were the preferred option because they allowed for more individualised instruction time and increased teacher attention to students' diverse needs. It should be noted that these studies were few in number and took place in very diverse contexts and across a large time span. There is a need for more qualitative research into the views and experiences of teachers, parents, and school administrators with special education class sizes in different local contexts and across various provision models. But most importantly, future research should strive to represent the voices of children and young people with special needs since they are the experts when it comes to matters concerning their own lives.

Occupational health and safety regulatory interventions to improve the work environment: An evidence and gap map of effectiveness studies.

Background: Unsafe and unhealthy working conditions lead to injuries and financial losses across the globe, resulting in a need for research into effective work environment interventions. Objectives: The objective of this evidence and gap map (EGM) is to provide an overview of existing systematic reviews and primary studies examining the effects of occupational health and safety regulatory interventions. Search Methods: Relevant studies are identified through searches in published and unpublished literature performed up to January 2023. Selection Criteria: The population for this EGM is workers above the age of 15 and their workplaces within the OECD. We include randomised controlled trials, non-randomised studies with a comparison of two or more groups of participants, and systematic reviews of effects. Data Collection and Analysis: The map has been populated based on information about interventions and outcomes, study design, OECD country, and publication status. We have performed critical appraisal of included systematic reviews using an adjusted version of the AMSTAR-2 tool. Main Results: The included studies for this report consist of six systematic reviews, 28 primary effect studies, and three on-going studies. The interactive map shows that the largest cluster of studies is located in the inspection activity domain, while the sickness absence outcome domain and the intervention categories for training initiatives and formulation of regulatory standards are only scarcely populated. Additionally, the AMSTAR-appraisal suggests a lack of rigorous systematic reviews and meta-analyses. Authors' Conclusions: More research in the form of primary studies and rigorous systematic reviews is needed to provide stakeholders with better guidance as to what constitutes the most efficient regulatory approaches to improve the work environment.

Outreach programs to improve life circumstances and prevent further adverse developmental trajectories of at-risk youth in OECD countries: A systematic review.

Background: At-risk youth may be defined as a diverse group of young people in unstable life circumstances, who are currently experiencing or are at risk of developing one or more serious problems. At-risk youth are often very unlikely to seek out help for themselves within the established venues, as their adverse developmental trajectories have installed a lack of trust in authorities such as child protection agencies and social workers. To help this population, a number of outreach programmes have been established seeking to help the young people on an ad hoc basis, meaning that the interventions are designed to fit the individual needs of each young person rather than as a one-size-fits-all treatment model. The intervention in this review is targeted outreach work which may be (but does not have to be) multicomponent programmes in which outreach may be combined with other services. Objectives: The main objective of this review was to answer the following research questions: What are the effects of outreach programmes on problem/high-risk behaviour of young people between 8 and 25 years of age living in OECD countries? Are they less likely to experience an adverse outcome such as school failure or drop-out, runaway and homelessness, substance and/or alcohol abuse, unemployment, long-term poverty, delinquency and more serious criminal behaviour? Search Methods: We identified relevant studies through electronic searches of bibliographic databases, governmental and grey literature repositories, hand search in specific targeted journals, citation tracking, and Internet search engines. The database searches were carried out in September 2020 and other resources were searched in October and November 2021. We searched to identify both published and unpublished literature, and reference lists of included studies and relevant reviews were searched. Selection Criteria: The intervention was targeted outreach work which may have been combined with other services. Young people between 8 and 25 years of age living in OECD countries, who either have experienced or is at-risk of experiencing an adverse outcome were eligible. Our primary focus was on measures of problem/high-risk behaviour and a secondary focus was on social and emotional outcomes. All study designs that used a well-defined control group were eligible for inclusion. Studies that utilised qualitative approaches were not included. Data Collection and Analysis: The total number of potentially relevant studies constituted 17,659 hits. A total of 16 studies (17 different interventions) met the inclusion criteria. Only five studies could be used in the data synthesis. Eight studies could not be used in the data synthesis as they were judged to have critical risk of bias and, in accordance with the protocol, were excluded from the meta-analysis on the basis that they would be more likely to mislead than inform. Two studies (three interventions) did not provide enough information enabling us to calculate an effect size and standard error, and one study did not provide enough information to assess risk of bias. Meta-analysis of all outcomes were conducted on each conceptual outcome separately. All analyses were inverse variance weighted using random effects statistical models incorporating both the sampling variance and between study variance components into the study level weights. Random effects weighted mean effect sizes were calculated using 95% confidence intervals. Too few studies were included to carry out any sensitivity analyses. Main Results: Four of the five studies used for meta analysis were from the USA and one was from Canada. The timespan in which included studies were carried out was 32 years, from 1985 to 2017; on average the intervention year was 2005. The average number of participants in the analysed interventions was 116, ranging from 30 to 346 and the average number of controls was 81, ranging from 32 to 321. At most, the results from two studies could be pooled in a single meta-analysis. It was only possible to pool the outcomes drug (other than marijuana) use, marijuana use and alcohol use each at two different time points (one and 3 months follow up). At 1 month follow up the weighted averages varied between zero and 0.05 and at 3 months follow up between -0.17 and 0.07. None of them were statistically significant. In addition, a number of other outcomes were reported in a single study only. Authors' Conclusions: Overall, there were too few studies included in any of the meta-analyses in order for us to draw any conclusion concerning the effectiveness of outreach. The vast majority of studies were undertaken in the USA. The dominance of the USA as the main country in which outreach interventions meeting our inclusion criteria have been evaluated using rigorous methods and within our specific parameters clearly limits the generalisability of the findings. None of the studies, however, was considered to be of overall high quality in our risk of bias assessment and the process of excluding studies with critical risk of bias from the meta-analysis applied in this review left us with only five of a total of 16 possible studies to synthesise. Further, because too few studies reported results on the same type of outcome at most two studies could be combined in a particular meta-analysis. Given the limited number of rigorous studies available from countries other than the USA, it would be natural to consider conducting a series of randomised controlled trials evaluating the effectiveness of outreach for at-risk youth in countries outside the USA. The trial(s) should be designed, conducted and reported according to methodological criteria for rigour in respect of internal and external validity to achieve robust results and preferably reporting a larger number of outcomes.

The effects of inclusion on academic achievement, socioemotional development and wellbeing of children with special educational needs.

Background: Considering the rapid global movement towards inclusion for students with special educational needs (SEN), there is a surprising lack of pedagogical or didactic theories regarding the ways in which inclusive education may affect students with SEN. Group composition within the educational setting may play a role in determining the academic achievement, socio-emotional development, and wellbeing of students with SEN. Proponents of inclusion propose that segregated educational placement causes stigmatisation and social isolation which may have detrimental effects on the self-concept and self-confidence of students with SEN. On the other hand, opponents of inclusion for all special needs students suggest that placement in general education classrooms may have adverse effects especially if the time and resources allocated for individualisation are not aligned with student needs. Since the 1980s, a number of reviews on the effects of inclusion have been published. Results are inconsistent, and several reviews point to a number of methodological challenges and weaknesses of the study designs within primary studies. In sum, the impact of inclusion on students with SEN may be hypothesised to be both positive and negative, and the current knowledge base is inconsistent. Objectives: The objective was first: To uncover and synthesise data from contemporary studies to assess the effects of inclusion on measures of academic achievement, socio-emotional development, and wellbeing of children with special needs when compared to children with special needs who receive special education in a segregated setting.A secondary objective was to explore how potential moderators (gender, age, type and severity of special need, part or full time inclusive education, and co-teaching) relate to outcomes. Search Methods: Relevant studies were identified through electronic searches in Academic Search Premier (EBSCO), APA PsycINFO (EBSCO), EconLit (EBSCO), ERIC (EBSCO), International Bibliography of the Social Sciences (ProQuest), Sociological Abstracts (ProQuest), Science Citation Index Expanded (Web Of Science), Social Sciences Citation Index (Web Of Science), and SocINDEX (EBSCO). The database searches were completed on 24 April 2021 and other resources: grey literature repositories, hand search in targeted journals and Internet search engines were searched in August/September 2021. The search was limited to studies reported after 2000. Selection Criteria: The review included studies of children with special needs in grades K to 12 in the OECD countries. Children with all types of verifiable SEN were eligible. Inclusion refers to an educational setting with a mixture of children with and without SEN. Segregation refers to the separate education of children with SEN. All studies that compared inclusive versus segregated educational settings for children with SEN were eligible. Qualitative studies were not included. Data Collection and Analysis: The total number of potentially relevant studies constituted 20,183 hits. A total of 94 studies met the inclusion criteria, all were non-randomised studies. The 94 studies analysed data from 19 different countries. Only 15 studies could be used in the data synthesis. Seventy-nine studies could not be used in the data synthesis as they were judged to be of critical risk of bias and, in accordance with the protocol, were excluded from the meta-analysis on the basis that they would be more likely to mislead than inform. The 15 studies came from nine different countries. Separate meta-analyses were conducted on conceptually distinct outcomes. All analyses were inverse variance weighted using random effects statistical models. Sensitivity analyses were performed to evaluate the robustness of pooled effect sizes across components of risk of bias. Main Results: The average baseline year of the interventions analysed in the 15 studies used for meta-analysis was 2006, ranging from 1998 to 2012. The average number of participants analysed in the interventions was 151, ranging from 10 to 1357, and the average number of controls was 261, ranging from 5 to 2752. The studies included children with multiple types of disabilities such as learning disorders/intellectual disabilities, autism spectrum disorders, ADHD, physical handicaps, visual impairments, and Down syndrome. At most, the results from eight studies could be pooled in any of the meta-analyses. All the meta-analyses showed a weighted average that favoured the intervention group. None of them were statistically significant. The random effects weighted standardised mean difference was 0.20 (95% confidence interval [CI]: -0.01 to 0.42) for overall psychosocial adjustment; 0.04 (95% CI: -0.27 to 0.35) for language and literacy learning outcomes, and 0.05 (95% CI: -0.16 to 0.26) for math learning outcomes. There were no appreciable changes in the results as indicated by the sensitivity analyses. There was some inconsistency in the direction and magnitude of the effect sizes between the primary studies in all analyses and a moderate amount of heterogeneity. We attempted to investigate the heterogeneity by single factor sub-group analyses, but results were inconclusive. Authors' Conclusions: The overall methodological quality of the included studies was low, and no experimental studies in which children were randomly assigned to intervention and control conditions were found. The 15 studies, which could be used in the data synthesis, were all, except for one, judged to be in serious risk of bias. Results of the meta-analyses do not suggest on average any sizeable positive or negative effects of inclusion on children's academic achievement as measured by language, literacy, and math outcomes or on the overall psychosocial adjustment of children. The average point estimates favoured inclusion, though small and not statistically significant, heterogeneity was present in all analyses, and there was inconsistency in direction and magnitude of the effect sizes. This finding is similar to the results of previous meta-analyses, which include studies published before 2000, and thus although the number of studies in the current meta-analyses is limited, it can be concluded that it is very unlikely that inclusion in general increases or decreases learning and psychosocial adjustment in children with special needs. Future research should explore the effects of different kinds of inclusive education for children with different kinds of special needs, to expand the knowledge base on what works for whom.

Parenting interventions to support parent/child attachment and psychosocial adjustment in foster and adoptive parents and children: A systematic review.

Background: Adopted children and children placed in foster care are at increased risk of developing a range of mental health, behavioural, and psychosocial adjustment problems. Previous studies suggest that due to early experiences of separation and loss some children may have difficulties forming a secure attachment relationship with the adoptive/foster parents. Objectives: The objectives of the present review were: (1) to assess the efficacy of attachment-based interventions on measures of favourable parent/child outcomes (attachment security, dyadic interaction, parent/child psychosocial adjustment, behavioural and mental health problems, and placement breakdown) within foster and adoptive families with children aged between 0 and 17 years. (2) to identify factors that appear to be associated with more effective outcomes and factors that modify intervention effectiveness (e.g., age of the child at placement and at intervention start, programme duration, programme focus). Search Methods: Relevant studies were identified through electronic searches of bibliographic databases, governmental and grey literature repositories, hand search in specific targeted journals, citation tracking, contact to international experts and Internet search engines. The database searches were carried out to October 2020. Selection Criteria: The interventions of interest were parenting interventions aimed at helping the foster/adopted children and their parents to form or sustain a secure attachment relationship. The interventions had to be at least partly informed by attachment theory. Data Collection and Analysis: The total number of potentially relevant studies constituted 17.822 hits after duplicates were removed. A total of 44 studies (27 different populations) met the inclusion criteria and were critically appraised by the review authors. Due to critical study quality, missing numeric data and re-use of the same data, only 24 studies analysing 16 different populations could be used in the data synthesis (children, N = 1302; parents, N = 1344). Meta-analysis using both child and parent outcomes were conducted on each metric separately. All analyses were inverse variance weighted using random effects statistical models. Random effects weighted mean effect sizes were calculated using 95% confidence intervals (CIs). When possible, we conducted moderator analysis using meta-regression and single factor sub group moderator analysis. Sensitivity analysis were conducted across study design and domains of the risk of bias assessment. Main Results: Ten studies analysed the effect of attachment-based interventions on the overall psychosocial adjustment of foster or adopted children as reported by their caregivers post intervention. Measures used include the Child Behaviour Checklist, The Strengths and Difficulties Questionnaire, Brief Infant-Toddler Social and Emotional Assessment (BITSEA) and Eyberg Child Behaviour Inventory. The random effects weighted standardised mean difference (SMD) favouring the intervention group was 0.37 (95% CI, 0.10-0.65) and statistically significant. Three studies analysed the effects of attachment-based interventions on the observed attachment security of foster and adopted children as measured by independent observation. Measures include the Strange Situation Procedure, Attachment Q-Set, and The Emotional Availability Clinical Screener. The random effects weighted SMD was 0.59 (95% CI, -0.40-1.57) and not statistically significant. Four studies analysed the effect of attachment-based interventions on positive child behaviour post intervention as measured by independent observation of video-taped interaction between the child and caregivers. Measures include Disruptive Behaviour Diagnostic Observation Schedule (DB-DOS) and Emotional Availability Scales). The random effects weighted SMD was 0.39 (95% CI, 0.14-0.64) and statistically significant. Ten studies analysed the effect of attachment-based interventions on positive parenting behaviour post intervention as measured by independent observation of video-taped interaction between the child and caregivers or coding of audio-taped recordings of parental speech. Measures include Adapted Ainsworth Scales for sensitivity and noninterference, Measurement of Empathy in Adult-Child Interaction, The Dyadic Parent-Child Interaction Coding System, Reflective functioning scale, and Emotional Availability Scales. The random effects weighted SMD was 1.56 (95% CI, 0.81-2.31) and statistically significant. Nine studies analysed the effect of attachment-based interventions on self-reported post intervention parenting stress (Parenting Stress Index). The random effects weighted SMD was 0.24 (95% CI, 0.03-0.46.) and statistically significant. Three studies analysed the effect of attachment-based interventions on parental post intervention self-reported depressive symptoms (Beck Depression Inventory). The random effects weighted SMD was 0.59 (95% CI, -0.08-1.25.) and not statistically significant. Follow-up analyses were carried out for the outcomes externalising behaviour, positive parenting, and parenting stress, but due to the low number of studies, results should be viewed with caution. Results of the single factor sub group moderator analysis suggest that it cannot be ruled out the effects differ depending on whether the interventions take place in the family home or in a clinical setting. However, it is unclear which location is associated with more positive effects as our findings differ between child and parent outcomes. Results of the sensitivity analysis showed no appreciable changes in the results following the removal of any of the studies in any of the analyses. Authors' Conclusions: Parenting interventions based on attachment theory increase positive parent/child interactional behaviours, decrease parenting stress, and increase the overall psychosocial adjustment of children in foster and adoptive families postintervention. Due to the low number of studies evidence regarding the effects of attachment-based parenting interventions on attachment security and disorganised attachment in foster and adopted children was inconclusive. Theoretically, it is possible that child attachment security and/or attachment disorganisation cannot change within the relatively short period of time that parenting interventions typically last. It is possible that if postintervention improvements in parenting behaviours are sustained over time, it may lead to possible improvement in child attachment security and a decrease in child disorganised attachment. Thus, more longitudinal research is needed. Furthermore, evidence regarding the long-term effects of attachment-based parenting interventions on any outcomes was inconclusive due to too few studies, but findings suggest that attachment-based interventions increase positive parenting behaviour at follow-up points 3-6 months after the intervention. No study included in the present review provided a measure of placement stability or breakdown as an outcome, which could be used in the meta-analysis. This further emphasises the need for future longitudinal research in prevention of placement breakdown.

Service learning for improving academic success in students in grade K to 12: A systematic review.

Background: School-based service-learning is a teaching strategy that explicitly links community service to academic instruction. It is distinctive from traditional voluntarism or community service in that it intentionally connects service activities with curriculum concepts and includes structured time for reflection. Service learning, by connecting education to real world issues and allowing students to address problems they identify, may be particularly efficacious as it increases engagement and motivates students, in particular students who might not respond well to more traditional teaching methods. Objectives: The main objective was to answer the following research question: What are the effects of service learning on academic success, neither employed, nor in education or training (NEET) status post compulsory school, personal and social skills, and risk behaviour of students in primary and secondary education (grades kindergarten to 12)? Further, we wanted to investigate study-level summaries of participant characteristics (e.g., gender, age or socioeconomic level) and quality of the service learning programme. Search Methods: We identified relevant studies through electronic searches of bibliographic databases, governmental and grey literature repositories, hand search in specific targeted journals, citation tracking, and Internet search engines. The database searches were carried out in November 2019 and other resources were searched in October 2020. We searched to identify both published and unpublished literature, and reference lists of included studies and relevant reviews were searched. Selection Criteria: The intervention was service learning which can be described as a curriculum-based community service that integrates classroom instruction (such as classroom discussions, presentations, or directed writing) with community service activities. We included children in primary and secondary education (grades kindergarten to 12) in general education. Our primary focus was on measures of academic success and NEET status. A secondary focus was on measures of personal and social skills, and risk behaviour (such as drug and alcohol use, violent behaviour, sexual risk taking). All study designs that used a well-defined control group were eligible for inclusion. Studies that utilised qualitative approaches were not included. Data Collection and Analysis: The total number of potentially relevant studies constituted 13,719 hits. A total of 37 studies met the inclusion criteria. The 37 studies analysed 30 different populations. Only 10 studies (analysing nine different populations) could be used in the data synthesis. Eighteen studies could not be used in the data synthesis as they were judged to have critical risk of bias and, in accordance with the protocol, were excluded from the meta-analysis on the basis that they would be more likely to mislead than inform. Five studies did not provide enough information enabling us to calculate an effects size and standard error, and one study did not provide enough information to assess risk of bias. Finally, two clusters of studies used the same data sets, resulting in an additional three studies we did not use in the data synthesis. Meta-analysis of all outcomes were conducted on each conceptual outcome separately. All analyses were inverse variance weighted using random effects statistical models incorporating both the sampling variance and between study variance components into the study level weights. Random effects weighted mean effect sizes were calculated using 95% confidence intervals. We carried out a sensitivity analysis to examine the impact of correcting for clustered assignment of treatments. Main Results: The 10 studies (analysing nine different populations) used for meta analysis were all from the United States. The timespan in which included studies were carried out was 33 years, from 1980 to 2013; on average the intervention year was 2007. The average number of participants in the analysed service learning interventions was 937, ranging from 18 to 3556 and the average number of controls was 927, ranging from 20 to 3395. At most, the results from three studies could be pooled in any of the meta-analyses. All the meta-analyses showed a weighted average that favoured the intervention group except the pregnancy outcome. None of them was statistically significant except the weighted average of the two studies reporting math test results. The random effects weighted standardised mean difference was 0.09 [95% confidence interval (CI): -0.02 to 0.21] for students' general grade point average; 0.04 (95% CI: -0.08 to 0.16) for reading; 0.21 (95% CI: 0.09 to 0.33) for math; 0.03 (95% CI: -0.10 to 0.16) for days absent from school; 0.13 (95% CI: -0.14 to 0.40) for self-esteem; 0.07 (95% CI: -0.04 to 0.18) for locus of control. The random effects weighted odds ratio was 1.05 (95% CI: 0.63 to 1.74) for pregnancy and 0.96 (95% CI: 0.74 to 1.25) for sexual risk behaviour. In addition, a number of other outcomes were reported in a single study only. There were no appreciable changes in the results as indicated by the sensitivity analysis. We did not find any adverse effects. Authors' Conclusions: In this review, we aimed to find evidence of the effectiveness of service learning on students' academic success, personal and social skills, and risk behaviour. However, the evidence was inconclusive. We found only few randomised controlled trials and the risk of bias in the included non-randomised studies was very high. All available evidence used in the data synthesis was US-based. The majority of studies available for meta-analysis reported on a very limited number of outcomes; in particular few reported results on students' academic success even though the outcome was collected. Further, the majority of studies used in the meta-analyses reported implementation problems. These considerations point to the need for more rigorously conducted studies performed outside the United States, reporting a larger number of outcomes. It would be natural to consider conducting a series of randomised controlled trial with specific allocation to implementation of high-quality service learning as guided by the eight standards: (1) Meaningful service, (2) Link to curriculum, (3) Reflection, (4) Diversity, (5) Youth voice, (6) Community partnerships, (7) Progress monitoring and (8) Sufficient duration and intensity. Specific attention would also have to be paid to stringency in terms of conducting a well-designed randomised trial with low risk of bias and ensuring that the sample sizes are large enough to enable sufficient power.

PROTOCOL: Occupational health and safety regulatory interventions to improve the work environment: An evidence and gap map of effectiveness studies.

This is the protocol for a Campbell systematic review. The objectives are as follows: provide an overview of the existing evidence base by identifying available systematic reviews and primary effectiveness studies, identify clusters of evidence suitable for a systematic review and identify gaps in evidence where primary research is needed.

PROTOCOL: The effects of small class sizes on students' academic achievement, socioemotional development, and well-being in special education.

This is the protocol for a Campbell review. The objective of this systematic review is to uncover and synthesise data from studies to assess the impact of small class sizes on the academic achievement, socioemotional development, and well-being of students with special educational needs. Where possible, we will also investigate the extent to which the effects differ among subgroups of students. Furthermore, we will perform a qualitative exploration of the experiences of children, teachers, and parents with special education class sizes.

Targeted school-based interventions for improving reading and mathematics for students with or at risk of academic difficulties in Grades K-6: A systematic review.

Background: Low levels of numeracy and literacy skills are associated with a range of negative outcomes later in life, such as reduced earnings and health. Obtaining information about effective interventions for children with or at risk of academic difficulties is therefore important. Objectives: The main objective was to assess the effectiveness of interventions targeting students with or at risk of academic difficulties in kindergarten to Grade 6. Search Methods: We searched electronic databases from 1980 to July 2018. We searched multiple international electronic databases (in total 15), seven national repositories, and performed a search of the grey literature using governmental sites, academic clearinghouses and repositories for reports and working papers, and trial registries (10 sources). We hand searched recent volumes of six journals and contacted international experts. Lastly, we used included studies and 23 previously published reviews for citation tracking. Selection Criteria: Studies had to meet the following criteria to be included: Population: The population eligible for the review included students attending regular schools in kindergarten to Grade 6, who were having academic difficulties, or were at risk of such difficulties. Intervention: We included interventions that sought to improve academic skills, were conducted in schools during the regular school year, and were targeted (selected or indicated). Comparison: Included studies used an intervention-control group design or a comparison group design. We included randomised controlled trials (RCT); quasi-randomised controlled trials (QRCT); and quasi-experimental studies (QES). Outcomes: Included studies used standardised tests in reading or mathematics. Setting: Studies carried out in regular schools in an OECD country were included. Data Collection and Analysis: Descriptive and numerical characteristics of included studies were coded by members of the review team. A review author independently checked coding. We used an extended version of the Cochrane Risk of Bias tool to assess risk of bias. We used random-effects meta-analysis and robust-variance estimation procedures to synthesise effect sizes. We conducted separate meta-analyses for tests performed within three months of the end of interventions (short-term effects) and longer follow-up periods. For short-term effects, we performed subgroup and moderator analyses focused on instructional methods and content domains. We assessed sensitivity of the results to effect size measurement, outliers, clustered assignment of treatment, risk of bias, missing moderator information, control group progression, and publication bias. Results: We found in total 24,414 potentially relevant records, screened 4247 of them in full text, and included 607 studies that met the inclusion criteria. We included 205 studies of a wide range of intervention types in at least one meta-analysis (202 intervention-control studies and 3 comparison designs). The reasons for excluding studies from the analysis were that they had too high risk of bias (257), compared two alternative interventions (104 studies), lacked necessary information (24 studies), or used overlapping samples (17 studies). The total number of student observations in the analysed studies was 226,745. There were 93% RCTs among the 327 interventions we included in the meta-analysis of intervention-control contrasts and 86% were from the United States. The target group consisted of, on average, 45% girls, 65% minority students, and 69% low-income students. The mean Grade was 2.4. Most studies included in the meta-analysis had a moderate to high risk of bias.The overall average effect sizes (ES) for short-term and follow-up outcomes were positive and statistically significant (ES = 0.30, 95% confidence interval [CI] = [0.25, 0.34] and ES = 0.27, 95% CI = [0.17, 0.36]), respectively). The effect sizes correspond to around one third to one half of the achievement gap between fourth Grade students with high and low socioeconomic status in the United States and to a 58% chance that a randomly selected score of an intervention group student is greater than the score of a randomly selected control group student.All measures indicated substantial heterogeneity across short-term effect sizes. Follow-up outcomes pertain almost exclusively to studies examining small-group instruction by adults and effects on reading measures. The follow-up effect sizes were considerably less heterogeneous than the short-term effect sizes, although there was still statistically significant heterogeneity.Two instructional methods, peer-assisted instruction and small-group instruction by adults, had large and statistically significant average effect sizes that were robust across specifications in the subgroup analysis of short-term effects (ES around 0.35-0.45). In meta-regressions that adjusted for methods, content domains, and other study characteristics, they had significantly larger effect sizes than computer-assisted instruction, coaching of personnel, incentives, and progress monitoring. Peer-assisted instruction also had significantly larger effect sizes than medium-group instruction. Besides peer-assisted instruction and small-group instruction, no other methods were consistently significant across the analyses that tried to isolate the association between a specific method and effect sizes. However, most analyses showed statistically significant heterogeneity also within categories of instructional methods.We found little evidence that effect sizes were larger in some content domains than others. Fractions had significantly higher associations with effect sizes than all other math domains, but there were only six studies of interventions targeting fractions. We found no evidence of adverse effects in the sense that no method or domain had robustly negative associations with effect sizes.The meta-regressions revealed few other significant moderators. Interventions in higher Grades tend to have somewhat lower effect sizes, whereas there were no significant differences between QES and RCTs, general tests and tests of subdomains, and math tests and reading tests. Authors' Conclusions: Our results indicate that interventions targeting students with or at risk of academic difficulties from kindergarten to Grade 6 have on average positive and statistically significant short-term and follow-up effects on standardised tests in reading and mathematics. Peer-assisted instruction and small-group instruction are likely to be effective components of such interventions.We believe the relatively large effect sizes together with the substantial unexplained heterogeneity imply that schools can reduce the achievement gap between students with or at risk of academic difficulties and not-at-risk students by implementing targeted interventions, and that more research into the design of effective interventions is needed.

Voluntary work for the physical and mental health of older volunteers: A systematic review.

Background: The increasing imbalance between the number of older adults not working and the number of adults in the age range of labour force participation (age range 20-64) has long been a fundamental public policy challenge in the Organization for Economic Co-operation and Development member countries. At a societal level, this growing imbalance raises serious concerns about the viability and funding of social security, pensions and health programmes. At an individual level, the concern is probably more that of aging well with the prospect of many years in retirement. Some research suggests that retiring for some carries the risk of a fast decline in health. Volunteering can play a significant role in people's lives as they transition from work to retirement, as it offers a "structured" means of making a meaningful contribution in society once the opportunity to do so through work has been cut off. Some older people consider voluntary work as a way to replicate aspects of paid work lost upon retirement, such as organisational structure and time discipline. In many countries, volunteering of the older adults is increasing and programmes designed specifically for this subpopulation are emerging. Volunteering may contribute to both individuals aging well and society aging well, as volunteering by the older adults at the same time relieves the societal burden if it helps maintain health and functionality for those who volunteer. It thus remains to be established to what extent volunteering impacts on the physical and mental health of those who volunteer. Objectives: The main objective of this review is to answer the following research question: what are the effects of volunteering on the physical and mental health of people aged 65 years or older? Search Strategy: Relevant studies were identified through electronic searches of bibliographic databases, governmental and grey literature repositories, hand search in specific targeted journals, citation tracking, contact to international experts and internet search engines. The database searches were carried out to December 2018 and other resources were searched in September 2019 and October 2019. We searched to identify both published and unpublished literature. The searches were international in scope. Reference lists of included studies and relevant reviews were also searched. Selection Criteria: The intervention of interest was formal volunteering which can be described as voluntary, on-going, planned, helping behaviour that intend to increase the well-being of strangers, offers no monetary compensation and typically occurs within an organisational context. We included older people aged 65 or over who are engaged in formal voluntary work. The primary focus was on measures of physical and mental health. All study designs that used a well-defined control group were eligible for inclusion. Studies that utilised qualitative approaches were not included. Data Collection and Analysis: The total number of potential relevant studies constituted 17,046 hits. A total of 90 studies, met the inclusion criteria and were critically appraised by the review authors. The 90 studies analysed 47 different populations. Only 26 studies (analysing 19 different populations) could be used in the data synthesis. Forty-six studies could not be used in the data synthesis as they were judged to have too high risk of bias and, in accordance with the protocol, were excluded from the meta-analysis on the basis that they would be more likely to mislead than inform. Eighteen studies did not provide enough information enabling us to calculate an effects size and standard error or did not provide results in a form enabling us to use it in the data synthesis. Finally, of the 26 studies that could be used in the data synthesis, two pairs of studies used the same two data sets and reported on the same outcome(s), thus in addition two studies were not used in the data synthesis.Meta-analysis of both physical health outcomes and mental health outcomes were conducted on each metric separately. All analyses were inverse variance weighted using random effects statistical models that incorporate both the sampling variance and between study variance components into the study level weights. Random effects weighted mean effect sizes were calculated using 95% confidence intervals (CIs).Sensitivity analysis was carried out by restricting the meta-analysis to a subset of all studies included in the original meta-analysis and was used to evaluate whether the pooled effect sizes were robust across components of risk of bias. Results: The 24 studies (analysing 19 different populations), used for meta analysis were from Australia, Ireland, Israel, Japan, Korea and United States, three were a randomised controlled trial and 21 were NRS. The baseline time period (the year the voluntary work that was analysed was measured) spanned by the included studies is 30 years, from 1984 to 2014 and on average the baseline year was 2001. On average the number of follow up years was 5, although with great variation from 0 to 25 years. The average number of volunteers analysed (not reported in four studies) was 2,369, ranging from 15 to 27,131 and the average number of controls was 13,581, ranging from 13 to 217.297. In total the average number of participants analysed was 14,566, ranging from 28 to 244.428.Ten studies analysed the effect of voluntary work on mortality, however, eight studies reported a hazard ratio and two studies reported an odds ratio. We analysed these two types of effect sizes separately. A hazard ratio <1 indicates that the treated, the volunteers is favoured. That is, the conditional mortality rate is lower for volunteers. All reported results indicated an effect favouring the volunteers, primary study effect sizes lied in the range 0.67-0.91. The random effects weighted mean hazard ratio was 0.76 (95% CI, 0.72-0.80) and statistically significant. The two studies that reported odds ratios of mortality supported this result. There was no heterogeneity between the studies in either of the meta analyses.Three studies analysed the effect of voluntary work on incident functional disability, using a hazard ratio as effect measure. All reported results indicated an effect favouring the volunteers, primary study effect sizes lied in the range 0.70-0.99. The random effects weighted mean hazard ratio was 0.83 (95% CI, 0.72-0.97) and statistically significant. There was a small amount of heterogeneity between the studies.Two studies analysed the effect of voluntary work on decline in instrumental activities of daily living, using an odds ratio as effect measure. Both reported results indicated an effect favouring the volunteers (0.63 and 0.83). The random effects weighted mean odds ratio was 0.73 (95% CI, 0.53-1.01) and not statistically significant. There is no heterogeneity between the two studies.Three studies analysed the effect of voluntary work on maintenance of functional competence, using an odds ratio as effect measure. All reported results indicated an effect favouring the volunteers, primary study effect sizes lied in the range 0.67-0.83. The random effects weighted mean odds ratio was 0.81 (95% CI, 0.70-0.94) and statistically significant. There is no heterogeneity between the studies.In addition a number of other physical outcomes were reported in a single study only.Three studies analysed the effect of voluntary work on depression, and reported results that enabled the calculation of standardised mean difference (SMD) and variance. The effect sizes are measured such that a positive effect size favours the volunteers. All reported results indicated an effect favouring the volunteers, primary study effect sizes lied in the range 0.05-0.66. The random effects weighted SMD was 0.12 (95% CI, 0.00-0.23) and statistically significant. There is a very small amount of heterogeneity between the studies.In addition, a number of other mental health outcomes were reported in a single study only.We did not find any adverse effects.There were no appreciable changes in the results across components of risk of bias as indicated by the sensitivity analysis. Authors' Conclusions: The review aimed to examine effects on all types of physical and mental health outcomes. With the exception of mortality, there was insufficient evidence available. The available evidence, however, does suggest that there is an effect on the mortality of volunteers, although the effect is small. We found evidence that voluntary work reduces the mortality hazard of the volunteers aged 65 and above. The effect corresponds to a 43% chance of the volunteers dying first which should be compared to a fifty-fifty chance (50%) of dying first if the intervention had no effect. The evidence seems robust in the sense that we did not find any heterogeneity between the studies. As the intervention, unlike most other interventions in the social welfare area, is not costly, it could be prescribed to more older adults. In fact as the intervention in contrary to carrying a cost is a productive activity contributing directly to community well-being and has a positive effect on the volunteers it probably should be prescribed universally. However, due to the very nature of the intervention, it is voluntary and it cannot be prescribed. But more people could be encouraged to take up voluntary work if the opportunity was immediately available and visible.

PROTOCOL: Parenting interventions to support parent/child attachment and psychosocial adjustment in foster and adoptive parents and children: A systematic review.

This is the protocol for a Campbell review. The objectives are as follows: 1.To assess the efficacy of attachment-based interventions on measures of favourable parent/child outcomes (attachment security, dyadic interaction, parent/child psychosocial adjustment, behavioural and mental health problems and placement breakdown) within foster and adoptive families with children aged between 0 and 17 years.2.To identify factors that appear to be associated with more effective outcomes and factors that modify intervention effectiveness (for example, age of the child at placement and at intervention start, programme duration, programme focus).

Deployment of personnel to military operations: impact on mental health and social functioning.

This Campbell systematic review examines the effects of deployment on mental health. The review summarizes evidence from 185 studies. All studies used observational data to quantify the effect of deployment. This review includes studies that evaluate the effects of deployment on mental health. A total of 185 studies were identified. However, only 40 of these were assessed to be of sufficient methodological quality to be included in the final analysis. The studies spanned the period from 1993 to 2017 and were mostly carried out in the USA, UK and Australia. The studies all had some important methodological weaknesses. None of the included studies used experimental designs (random assignment). Deployment to military operations negatively affects the mental health functioning of deployed military personnel. For assessments taken more than 24 months since exposure, we consistently found adverse effects of deployment on all mental health domains (PTSD, depression, substance abuse/dependence, and common mental disorders), particularly on PTSD. For assessments taken less than 24 months (or a variable number of months since exposure) the evidence was less consistent and in many instances inconclusive. Plain language summary: Deployment to military operations negatively affects the mental health functioning of deployed military personnel: While additional research is needed, the current evidence strongly supports the notion that deployment negatively affects mental health functioning of deployed military personnel.What is this review about?: When military personnel are deployed to military operations abroad they face an increased risk of physical harm, and an increased risk of adverse shocks to their mental health.The primary condition under consideration is deployment to an international military operation. Deployment to a military operation is not a uniform condition; rather, it covers a range of scenarios. Military deployment is defined as performing military service in an operation at a location outside the home country for a limited time period, pursuant to orders.The review included studies that reported outcomes for individuals who had been deployed. This review looked at the effect of deployment on mental health outcomes. The mental health outcomes are: post-traumatic stress disorder (PTSD), major depressive disorder (MDD), common mental disorders (depression, anxiety and somatisation disorders) and substance-related disorders.By identifying the major effects of deployment on mental health and quantifying these effects, the review can inform policy development on deployment and military activity as well as post-deployment support for veterans. In this way the review enables decision-makers to prioritise key areas.What are the main findings of this review?: What studies are included?: This review includes studies that evaluate the effects of deployment on mental health. A total of 185 studies were identified. However, only 40 of these were assessed to be of sufficient methodological quality to be included in the final analysis. The studies spanned the period from 1993 to 2017 and were mostly carried out in the USA, UK and Australia. The studies all had some important methodological weaknesses. None of the included studies used experimental designs (random assignment).Does deployment have an effect on mental health?: Deployment to military operations negatively affects the mental health functioning of deployed military personnel. For assessments taken more than 24 months since exposure, we consistently found adverse effects of deployment on all mental health domains (PTSD, depression, substance abuse/dependence, and common mental disorders), particularly on PTSD. For assessments taken less than 24 months (or a variable number of months since exposure) the evidence was less consistent and in many instances inconclusive.What do the findings of this review mean?: The odds of screening positive for PTSD and depression were consistently high in the longer term. This suggests that efforts should be increased to detect and treat mental disorders, as effects may be long-lasting.Overall the risk of bias in the majority of included studies was high. While it is difficult to imagine a randomised study design to understand how deployment affects mental health, other matters such as changes to personnel policy, or unanticipated shocks to the demand for military personnel, could potentially be a rich source of quasi-experimental variation.How up-to-date is this review?: The review authors searched for studies up to 2017. This Campbell systematic review was published in March 2018. Executive summary: BACKGROUND: When military personnel are deployed to military operations abroad they face an increased risk of physical harm, and an increased risk of adverse shocks to their mental health. Research suggests that the increased risk to mental health is mainly due to the hazards of war, combat exposure: firing weapons, road side bombs, seeing fellow soldiers, friends, civilians, and enemies being injured, maimed or killed. These experiences may lead to severe mental stress. The adverse impact on mental health is the psychological cost of war, and it is of interest to policymakers to learn the magnitude of these effects. This review sets out to synthesise available evidence about the consequences of deployment for deployed military personnel in the mental health and social functioning domains.OBJECTIVES: The objective of this review isto synthesise the consequences of deployment to military operation on the mental health and social functioning of deployed military personnel.SEARCH METHODS: We searched electronic databases, grey literature, and references from primary studies and related reviews. No language or date restrictions were applied to the searches. We searched the following electronic databases: Academic Search Elite, Cochrane Library, EMBASE, ERIC, MEDLINE, PsycINFO, Science Citation Index, Social Science Citation Index, SocINDEX, as well as the Nordic platforms: bibliotek.dk, BIBSYS, and LIBRIS. The conclusions of this review are based on the most recent searches performed. The last search was performed in April 2017.SELECTION CRITERIA: Primary studies had to meet the following inclusion criteria: Participants: The participants should be military personnel.Intervention: The condition should be deployment to a military operation.Comparison: The relevant comparisons were either comparing a) deployed military personnel to non-deployed military personnel, b) deployed military personnel to military personnel deployed elsewhere, for example personnel deployed to non-combat operations, c) military personnel deployed to the same operation but stratified by combat exposure.Outcomes: The study should report on one or more mental health outcomes, and/or social functioning for the deployed participants. In particular studies should report on one or more of the following mental health outcomes: PTSD, major depression, substance abuse or dependence (including alcohol), and common mental disorders (depression and anxiety disorders). The following social functioning outcomes were relevant: employment, and homelessness.Study Designs: Both experimental and quasi-experimental designs with a comparison group were eligible for inclusion in the review. Studies were excluded if they: Reported on deployments taking place before 1989.Used a within group pre-post study design.Did not report on at least one of the mental health or social functioning outcomes. DATA COLLECTION AND ANALYSIS: The total number of potentially relevant studies constituted31,049records. A total of 185 studies met the inclusion criteria and were critically appraised by the review authors. The final selection of 185 studies was from 13 different countries.Forty eight of the 185 studies did not report effect estimates or provide data that would allow the calculation of an effect size and standard error. Fifty four studies were excluded because of overlapping samples. The majority of those studies were from USA but the main reason for not using studies from USA in the synthesis was lack of information to calculate an effect size. Nearly half the studies from the UK could not be used in the synthesis due to overlap of data samples. Forty three studies were judged to have a very high risk of bias (5 on the scale) and, in accordance with the protocol, we excluded these from the data synthesis on the basis that they would be more likely to mislead than inform., Thus a total of 40 studies, from five different countries, were included in the data synthesis.Random effects models were used to pool data across the studies. We used the odds ratio. Pooled estimates were weighted with inverse variance methods, and 95% confidence intervals were calculated. The meta-analyses were carried out by time since exposure (short, medium, long, and other time since exposure) and by type of comparison (deployed versus non-deployed, all deployed but stratified by either combat operations versus non-combat operations, or stratified by combat exposure). We performed single factor subgroup analysis. The assessment of any difference between subgroups was based on 95% confidence intervals. Funnel plots were used to assess the possibility of publication bias. Sensitivity analysis was used to evaluate whether the pooled effect sizes were robust across components of methodological quality.MAIN RESULTS: The findings were mixed, depending on the outcome, the time since exposure and the approach (deployed versus non-deployed termed absolute or stratified by extent of combat termed relative) used to investigate the effect. It was not possible to analyse the outcomes homelessness and employment. All studies that could be used in the data synthesis reported on the impact of deployment on mental health; PTSD, depression, substance use or common mental disorder.For assessments taken less than 24 months since exposure the evidence was inconclusive either because too few studies reported results in the short and medium term and/or the degree of heterogeneity between studies was large.For assessments taken at other time points (a variable number of months since exposure) the evidence was inconclusive for the relative comparisons due to either too few studies or a substantial degree of heterogeneity between studies. For the absolute comparison the analysis of common mental disorder was inconclusive, whereas the average effects of PTSD and depression were positive and statistically significant (PTSD odds ratio (OR) was 1.91 (95% confidence interval (CI): 1.28 to 2.85) and OR=1.98 (95% CI: 1.05 to 3.70) for depression). The analysis concerning substance use indicated that deployed participants did not have higher odds of screening positive for substance use compared to non-deployed participants (OR=1.15 (95% CI: 0.98 to 1.36)).For assessments taken more than 24 months post exposure, meta-analyses indicated that the odds of screening positive for PTSD, depression, substance use and common mental disorder were higher for participants in the deployed group compared to participants in the group that were not deployed (PTSD OR=3.31 (95% CI: 2.69 to 4.07), OR=2.19 (95% CI: 1.58 to 3.03) for depression, OR=1.27 (95% CI: 1.15 to 1.39) for substance use, and OR=1.64 (95% CI: 1.38 to 1.96) for common mental disorder). Likewise, participants reporting high combat exposure had higher odds of screening positive for PTSD and depression than participants reporting lower exposure for long term assessments (PTSD OR=3.05 (95% CI: 1.94 to 4.80) and OR=1.81 (95% CI: 1.28 to 2.56) for depression). The analyses of substance use and common mental disorder were inconclusive due to too few studies.On the basis of the prevalence of mental health problems in pre-deployed or non-deployed population based comparison sampleswe would therefore expect the long term prevalence of PTSD in post-deployed samples to be in the range 6.1 - 14.9%, the long term prevalence of depression to be in the range from 7.6% to 18%, the long term prevalence of substance use to be in the range from 2.4% to 17.5% and the prevalence of common mental disorder to be in the range from 10% to 23%.Sensitivity analyses resulted in no appreciable change in effect size, suggesting that the results are robust.It was only possible to assess the impact of two types of personnel characteristics (branch of service and duty/enlistment status) on the mental health outcomes. We found no evidence to suggest that the effect of deployment on any outcomes differ between these two types of personnel characteristics.AUTHORS' CONCLUSIONS: Deployment to military operations negatively affects the mental health functioning of deployed military personnel. We focused on the effect of deployment on PTSD (post-traumatic stress disorder), depression, substance abuse/dependence, and common mental disorders (depression and anxiety disorders). For assessments taken less than 24 months (or a variable number of months since exposure) the evidence was less consistent and in many instances inconclusive. For assessments taken more than 24 months since exposure, we consistently found adverse effects of deployment on all domains, particularly on PTSD. There is increased political awareness of the need to address post deployment mental health problems. The odds of screening positive for PTSD and depression were consistently high in the longer term. This suggests that efforts should be increased to detect and treat mental disorders, as effects may be long lasting. Mental illness is of particular concern in the military for operational reasons, but they may be hard to detect in the military setting because a military career is intimately linked with mental and physical strength.It was not possible to examine a number of factors which we had reason to expect would impact on the magnitude of the effect. This would have been particularly relevant from a policy perspective because these are direct parameters that one could use to optimally "organize" deployment in order to minimize impacts on mental health functioning.While additional research is needed, the current evidence strongly supports the notion that deployment negatively affects mental health functioning of deployed military personnel. The next step is to begin to examine preventive measures and policies for organizing deployment, in order to minimize the effects on mental health.

Reducing unemployment benefit duration to increase job finding rates: a systematic review.

This Campbell systematic review examines the impact of reducing the maximum duration of unemployment benefits on job-finding rates. Seven studies were included in the review, all of which are from European countries. Included studies had to examine the effect of a reduction in the maximum duration of entitlement of any kind of unemployment benefits on employment using a well-defined control group. Whilst 41 studies were identified, after allowing for study quality and data issues, only seven studies were included in the review. The included studies covered Austria (2 studies), France, Germany (3 studies) and Slovenia. Maximum entitlement ranged between 26 and 209 weeks. The studies analyzed reductions between 9 and 179 weeks, with an average of 43 weeks. The studies analyze data from 1,154,090 unemployment spells. Reducing the duration of unemployment benefits increases the exit rate from unemployment. Data from seven studies show that the exit rate from unemployment for those with reduced duration of benefit entitlement on average is 10 per cent. This corresponds to a 52% chance that those with reduced duration will find a job before an unemployed person with the existing, longer duration (no effect corresponds to a 50% chance). There is not enough evidence to determine effects on the exit rate from re-employment or on the wage rate in the job found. There are insufficient high-quality studies to allow an examination of variation of effects. Plain language summary: Reducing the maximum duration of unemployment benefits increases the job finding rate of the unemployed: Reducing the maximum duration of unemployment benefits is one strategy used to reduce unemployment. Evidence from seven studies confirms such an effect. However, the effect is small and more studies of higher quality are needed to give more detailed findings to inform policy.The review in brief: Evidence from seven studies shows shortening the maximum duration of unemployment benefit entitlement has a small effect on the job finding rate of the unemployed.What is this review about?: Policymakers may wish to reduce the generosity of the unemployment benefits system in order to reduce unemployment levels. Reducing benefit levels may be politically more difficult than shortening the length of the unemployment benefit eligibility period to create work incentives for the unemployed.This review summarizes studies that measure the effects of shortening the maximum duration of unemployment benefit entitlement on job finding rates.What are the main findings of this review?: What studies are included?: Included studies had to examine the effect of a reduction in the maximum duration of entitlement of any kind of unemployment benefits on employment using a well-defined control group.Whilst 41 studies were identified, after allowing for study quality and data issues, only seven studies were included in the review. The included studies covered Austria (2 studies), France, Germany (3 studies) and Slovenia. Maximum entitlement ranged between 26 and 209 weeks. The studies analyzed reductions between 9 and 179 weeks, with an average of 43 weeks. The studies analyze data from 1,154,090 unemployment spells.What are the main results of this review?: Reducing the duration of unemployment benefits increases the exit rate from unemployment. Data from seven studies show that the exit rate from unemployment for those with reduced duration of benefit entitlement on average is 10 per cent. This corresponds to a 52% chance that those with reduced duration will find a job before an unemployed person with the existing, longer duration (no effect corresponds to a 50% chance).There is not enough evidence to determine effects on the exit rate from re-employment or on the wage rate in the job found. There are insufficient high-quality studies to allow an examination of variation of effects.What do the findings of this review mean?: On the basis of this limited number of studies, shortening the maximum duration of unemployment benefit entitlement has a small effect on the job finding rate of the unemployed. Whether unemployed workers responding to a shorter potential benefit entitlement may be worse off, in the sense that they accept "lower quality" jobs, has not yet been fully investigated.But the review finds a surprisingly low number of studies with a sufficiently low risk of bias to be used for synthesis to determine the effect size of shortening the maximum duration of unemployment benefit entitlement. Many studies had to be excluded as they had a high risk of bias. This is a finding in its own right.There is a need for future studies to more thoroughly discuss the assumptions of the study design and justify the choice of method by considering and reporting all relevant data and tests. Future studies should also use data with all relevant information, in particular, information on whether eligible individuals actually received unemployment benefits and information on individual maximum entitlement duration.How up-to-date is this review?: The review authors searched for studies published up to December 2016. This Campbell Systematic Review was published in February 2018. Executive Summary/Abstract: BACKGROUND: Unemployment benefit programmes protect individuals against loss of income and provide unemployed individuals with the possibility of finding a better match between their qualifications and job vacancies. However, unemployment benefits may also distort incentives by subsidizing long and unproductive job searches. In order to reduce unemployment levels, policymakers may wish to reduce the generosity of the unemployment system. While it may be politically intractable to lower the monetary amount of unemployment benefits available, the length of the unemployment benefit eligibility period is often used as a political instrument to create work incentives for the unemployed. If a shorter benefit period results in a significantly increased incentive for finding work, shortening the benefit eligibility period may reduce the share of long and unproductive job searches and thereby decrease the overall unemployment level.OBJECTIVES: The purpose of this review is to systematically uncover relevant studies in the literature that measure the effects of shortening the maximum duration of unemployment benefit entitlement on job finding rates, and to synthesize the effects in a transparent manner. As a secondary objective we will, where possible, investigate the extent to which the effects differ among different groups of unemployed people, such as those with high/low levels of education or men/women, and further explore from which point in the unemployment spell unemployed individuals react to the length of benefit entitlement.SEARCH METHODS: The search was concluded in March 2016. Relevant studies were identified through electronic searches of bibliographic databases, government policy databanks, internet search engines and hand searching of core journals. We searched to identify both published and unpublished literature. The searches were international in scope. Reference lists of included studies and relevant reviews were also searched.SELECTION CRITERIA: The intervention of interest was a reduction (change) in the maximum duration of entitlement of any kind of unemployment benefits. We included unemployed individuals who received any type of time-limited benefit during their unemployment spell. All study designs that used a well-defined control group were eligible for inclusion in this review. Studies that utilised qualitative approaches were not included in the review due to the absence of adequate control group conditions.DATA COLLECTION AND ANALYSIS: Random effects models were used to pool data across the studies. We used the point estimate of the hazard ratio. Pooled estimates were weighted with inverse variance methods, and 95% confidence intervals were used. A sensitivity analysis was performed to evaluate whether the pooled effect sizes were robust across components of methodological quality, in relation to the quality of data and whether the study analysed an extension of entitlement duration.RESULTS: The initial search for potentially relevant studies resulted in a total number of 34,930 hits. A total of 41 studies, consisting of 66 papers, from 15 different countries, met the inclusion criteria and were vetted by the review authors. Only 38 studies provided data that permitted the calculation of an effect size for the primary outcome. Of these 38 studies, 28 studies could not be used in the data synthesis due to a too high risk of bias. A further 3 studies could not be used in the data synthesis due to overlapping of data samples. As a result, only 7 studies were included in the data synthesis and one of these studies only provided results on the secondary outcome. In total, 6 studies provided data that permitted the calculation of an effect size for the primary outcome and 3 studies provided data that permitted the calculation of secondary outcome. The sample size used in the studies ranged from 5,017 spells of unemployment to 509,355 spells. The total number of unemployment spells was 1,154,090, implying an average sample size of 164,870 spells of unemployment per study.The seven studies covered Austria, France, Germany and Slovenia. There was a high degree of variation in maximum entitlement, ranging between 26 and 209 weeks. On average the studies analysed a reduction of 43 weeks in maximum entitlement; the smallest being a reduction of 9 weeks and the largest a reduction of 179 weeks. Four studies restricted the analysis to a specific age group and three studies restricted the analysis to specific work experience levels. All studies used non-randomised designs. In the majority of studies the risk of bias was high.This review found a statistically significant effect of shortening the maximum duration of unemployment benefit entitlement. The overall impact of shortening the maximum duration of unemployment benefit entitlement, obtained using hazard ratios, was estimated at 1.10 (95% CI 1.03 to 1.17, p=0.0005), which translates into an increase of approximately 10% in the exit rate from unemployment into employment and corresponds to a 52% chance that a treated unemployed person will find a job before a non-treated unemployed person.Thus, although small, the available evidence associated with a sufficiently low risk of bias supports the hypothesis of an incentive effect of shortening the maximum duration of unemployment benefit entitlement. There was a lack of evidence to conclude that shortening the maximum duration of unemployment benefit entitlement has an impact on the quality of the job obtained.Only three studies provided data on the exit rate from re-employment and three studies provided data on the log wage ratio in the re-employment job.The overall impact of shortening the maximum duration of unemployment benefit entitlement on the exit rate from the re-employment job, obtained using hazard ratios, was 0.99 (95% CI 0.97 to 1.02, p=0.64) and the overall wage ratio was 1.00 (95% CI 0.99 to 1.01, p=0.089).We did not find any adverse effects.Sensitivity analyses resulted in no appreciable change in effect size, suggesting that the results are robust. The limited number of studies used in the meta-analysis should, however, be considered when interpreting the results.Due to having an insufficient number of studies available for moderator analysis to be performed, it was not possible to examine whether the effect of reducing the maximum potential benefit duration on job-finding differs for men and women, for particular age groups or educational groups, or if factors such as good or bad labour market conditions, the type of unemployment benefit, the availability of alternative benefits, or whether compulsory activation is part of the institutional system, have an impact on the effect.AUTHORS' CONCLUSIONS: To the best of our knowledge, this is the first systematic review analysing the magnitude of the effect of shortening the maximum duration of unemployment benefit entitlement on the job finding rate. The review finds a surprisingly low number of studies with a sufficiently low risk of bias to enter a synthesis of the effect size of shortening the maximum duration of unemployment benefit entitlement. On the basis of this limited number of studies, shortening the maximum duration of unemployment benefit entitlement displays a limited potential for altering the employment prospects of the unemployed individuals. The available evidence does suggest an effect on the job finding rate of shortening the maximum duration of unemployment benefit entitlement, but the effect is small. Further, whether unemployed workers responding to a shorter potential benefit entitlement may be worse off, in the sense that they accept "lower quality"" jobs, has not yet been fully investigated.The number of studies used in the data synthesis (7) is relatively low compared to the large number of studies (41) meeting the inclusion criteria for the review. The reduction in studies eligible for inclusion in the data synthesis was primarily caused by a judgment of too high a risk of bias. Thus, the process of excluding studies with too high risk of bias from the meta-analysis applied in this review left us with only seven studies to synthesize. This is a finding in its own right, entailing important information for stakeholders on the degree of confidence to place on the expected gains from changing the maximum potential unemployment benefit duration; fewer studies with too high risk of bias would have provided a more robust literature on which to base conclusions. There is a need for future studies to more thoroughly discuss the identifying assumptions of the study design and justify the choice of method by considering and reporting all relevant data and tests. Further, future studies should rely on data where all relevant information is available, in particular information on whether eligible individuals actually received unemployment benefits and information on individual maximum entitlement duration.

Small class sizes for improving student achievement in primary and secondary schools: a systematic review.

This Campbell systematic review examines the impact of class size on academic achievement. The review summarises findings from 148 reports from 41 countries. Ten studies were included in the meta-analysis. Included studies concerned children in grades kindergarten to 12 (or the equivalent in European countries) in general education. The primary focus was on measures of academic achievement. All study designs that used a well-defined control group were eligible for inclusion. A total of 127 studies, consisting of 148 papers, met the inclusion criteria. These 127 studies analysed 55 different populations from 41 different countries. A large number of studies (45) analysed data from the Student Teacher Achievement Ratio (STAR) experiment which was for class size reduction in grade K-3 in the US in the eighties. However only ten studies, including four of the STAR programme, could be included in the meta-analysis. Overall, the evidence suggests at best a small effect on reading achievement. There is a negative, but statistically insignificant, effect on mathematics. For the non-STAR studies the primary study effect sizes for reading were close to zero but the weighted average was positive and statistically significant. There was some inconsistency in the direction of the primary study effect sizes for mathematics and the weighted average effect was negative and statistically non-significant. The STAR results are more positive, but do not change the overall finding. All reported results from the studies analysing STAR data indicated a positive effect of smaller class sizes for both reading and maths, but the average effects are small. Plain language summary: Small class size has at best a small effect on academic achievement: Reducing class size is seen as a way of improving student performance. But larger class sizes help control education budgets. The evidence suggests at best a small effect on reading achievement. There is a negative, but statistically insignificant, effect on mathematics, so it cannot be ruled out that some children may be adversely affected.What is this review about?: Increasing class size is one of the key variables that policy makers can use to control spending on education.But the consensus among many in education research is that smaller classes are effective in improving student achievement which has led to a policy of class size reductions in a number of US states, the UK, and the Netherlands. This policy is disputed by those who argue that the effects of class size reduction are only modest and that there are other more cost-effective strategies for improving educational standards.Despite the important policy and practice implications of the topic, the research literature on the educational effects of class-size differences has not been clear.This review systematically reports findings from relevant studies that measure the effects of class size on academic achievement.What are the main findings of this review?: What studies are included?: Included studies concerned children in grades kindergarten to 12 (or the equivalent in European countries) in general education. The primary focus was on measures of academic achievement. All study designs that used a well-defined control group were eligible for inclusion.A total of 127 studies, consisting of 148 papers, met the inclusion criteria. These 127 studies analysed 55 different populations from 41 different countries. A large number of studies (45) analysed data from the Student Teacher Achievement Ratio (STAR) experiment which was for class size reduction in grade K-3 in the US in the eighties. However only ten studies, including four of the STAR programme, could be included in the meta-analysis.What are the main results?: Overall, the evidence suggests at best a small effect on reading achievement. There is a negative, but statistically insignificant, effect on mathematics.For the non-STAR studies the primary study effect sizes for reading were close to zero but the weighted average was positive and statistically significant. There was some inconsistency in the direction of the primary study effect sizes for mathematics and the weighted average effect was negative and statistically non-significant.The STAR results are more positive, but do not change the overall finding. All reported results from the studies analysing STAR data indicated a positive effect of smaller class sizes for both reading and maths, but the average effects are small.What do the findings of this review mean?: There is some evidence to suggest that there is an effect of reducing class size on reading achievement, although the effect is very small. There is no significant effect on mathematics achievement, though the average is negative meaning a possible adverse impact on some students cannot be ruled out.The overall reading effect corresponds to a 53 per cent chance that a randomly selected score of a student from the treated population of small classes is greater than the score of a randomly selected student from the comparison population of larger classes. This is a very small effect.Class size reduction is costly. The available evidence points to no or only very small effect sizes of small classes in comparison to larger classes. Moreover, we cannot rule out the possibility that small classes may be counterproductive for some students. It is therefore crucial to know more about the relationship between class size and achievement in order to determine where money is best allocated.How up-to-date is this review?: The review authors searched for studies published up to February 2017. This Campbell systematic review was published in 2018. Executive Summary/Abstract: BACKGROUND: Increasing class size is one of the key variables that policy makers can use to control spending on education. Reducing class size to increase student achievement is an approach that has been tried, debated, and analysed for several decades. Despite the important policy and practice implications of the topic, the research literature on the educational effects of class-size differences has not been clear.The consensus among many in education research, that smaller classes are effective in improving student achievement has led to a policy of class size reductions in a number of U.S. states, the United Kingdom, and the Netherlands. This policy is disputed by those who argue that the effects of class size reduction are only modest and that there are other more cost-effective strategies for improving educational standards.OBJECTIVES: The purpose of this review is to systematically uncover relevant studies in the literature that measure the effects of class size on academic achievement. We will synthesize the effects in a transparent manner and, where possible, we will investigate the extent to which the effects differ among different groups of students such as high/low performers, high/low income families, or members of minority/non-minority groups, and whether timing, intensity, and duration have an impact on the magnitude of the effect.SEARCH METHODS: Relevant studies were identified through electronic searches of bibliographic databases, internet search engines and hand searching of core journals. Searches were carried out to February 2017. We searched to identify both published and unpublished literature. The searches were international in scope. Reference lists of included studies and relevant reviews were also searched.SELECTION CRITERIA: The intervention of interest was a reduction in class size. We included children in grades kindergarten to 12 (or the equivalent in European countries) in general education. The primary focus was on measures of academic achievement. All study designs that used a well-defined control group were eligible for inclusion. Studies that utilized qualitative approaches were not included.DATA COLLECTION AND ANALYSIS: The total number of potential relevant studies constituted 8,128 hits. A total of 127 studies, consisting of 148 papers, met the inclusion criteria and were critically appraised by the review authors. The 127 studies analysed 55 different populations from 41 different countries.A large number of studies (45) analysed data from the STAR experiment (class size reduction in grade K-3) and its follow up data.Of the 82 studies not analysing data from the STAR experiment, only six could be used in the data synthesis. Fifty eight studies could not be used in the data synthesis as they were judged to have too high risk of bias either due to confounding (51), other sources of bias (4) or selective reporting of results (3). Eighteen studies did not provide enough information enabling us to calculate an effects size and standard error or did not provide results in a form enabling us to use it in the data synthesis.Meta-analysis was used to examine the effects of class size on student achievement in reading and mathematics. Random effects models were used to pool data across the studies not analysing STAR data. Pooled estimates were weighted using inverse variance methods, and 95% confidence intervals were estimated. Effect sizes were measured as standardised mean differences (SMD). It was only possible to perform a meta-analysis by the end of the treatment year (end of the school year).Four of the studies analysing STAR data provided effect estimates that could be used in the data synthesis. The four studies differed in terms of both the chosen comparison condition and decision rules in selecting a sample for analysis. Which of these four studies' effect estimates should be included in the data synthesis was not obvious as the decision rule (concerning studies using the same data set) as described in the protocol could not be used. Contrary to usual practice we therefore report the results of all four studies and do not pool the results with the studies not analysing STAR data except in the sensitivity analysis. We took into consideration the ICC in the results reported for the STAR experiment and corrected the effect sizes and standard errors using ρ = 0.22. No adjustment due to clustering was necessary for the studies not analysing STAR data.Sensitivity analysis was used to evaluate whether the pooled effect sizes were robust across components of methodological quality, in relation to inclusion of a primary study result with an unclear sign, inclusion of effect sizes from the STAR experiment and to using a one-student reduction in class size in studies using class size as a continuous variable.RESULTS: All studies, not analysing STAR data, reported outcomes by the end of the treatment (end of the school year) only. The STAR experiment was a four year longitudinal study with outcomes reported by the end of each school year. The experiment was conducted to assess the effectiveness of small classes compared with regular-sized classes and of teachers' aides in regular-sized classes on improving cognitive achievement in kindergarten and in the first, second, and third grades. The goal of the STAR experiment was to have approximately 100 small classes with 13-17 students (S), 100 regular classes with 22-25 students (R), and 100 regular with aide classes with 22-25 students (RA).Of the six studies not analysing STAR, only five were used in the meta-analysis as the direction of the effect size in one study was unclear. The studies were from USA, the Netherlands and France, one was a RCT and five were NRS. The grades investigated spanned kindergarten to 3. Grade and one study investigated grade 10. The sample sizes varied; the smallest study investigated 104 students and the largest study investigated 11,567 students. The class size reductions varied from a minimum of one student in four studies, a minimum of seven students in another study to a minimum of 8 students in the last study.All outcomes were scaled such that a positive effect size favours the students in small classes, i.e. when an effect size is positive a class size reduction improves the students' achievement.Primary study effect sizes for reading lied in the range -0.08 to 0.14. Three of the study-level effects were statistically non-significant. The weighted average was positive and statistically significant. The random effects weighted standardised mean difference was 0.11 (95% CI 0.05 to 0.16) which may be characterised as small. There is some inconsistency in the direction of the effect sizes between the primary studies. Primary study effect sizes for mathematics lies in the range -0.41 to 0.11. Two of the study-level effects were statistically non-significant. The weighted average was negative and statistically non-significant. The random effects weighted standardised mean difference was -0.03 (95% CI -0.22 to 0.16). There is some inconsistency in the direction as well as the magnitude of the effect sizes between the primary studies.All reported results from the four studies analysing STAR data indicated a positive effect favouring the treated; all of the study-level effects were statistically significant. The study-level effect sizes for reading varied between 0.17 and 0.34 and the study-level effect sizes for mathematics varied between 0.15 and 0.33.There were no appreciable changes in the results when we included the extremes of the range of effect sizes from the STAR experiment. The reading outcome lost statistical significance when the effect size from the primary study reporting a result with an unclear direction was included with a negative sign and when the results from the studies using class size as a continuous variable were included with a one student reduction in class size instead of a standard deviation reduction in class size.Otherwise, there were no appreciable changes in the results.AUTHORS' CONCLUSIONS: There is some evidence to suggest that there is an effect of reducing class size on reading achievement, although the effect is very small. We found a statistically significant positive effect of reducing the class size on reading. The effect on mathematics achievement was not statistically significant, thus it is uncertain if there may be a negative effect.The overall reading effect corresponds to a 53 per cent chance that a randomly selected score of a student from the treated population of small classes is greater than the score of a randomly selected student from the comparison population of larger classes. The overall effect on mathematics achievement corresponds to a 49 per cent chance that a randomly selected score of a student from the treated population of small classes is greater than the score of a randomly selected student from the comparison population of larger classes.Class size reduction is costly and the available evidence points to no or only very small effect sizes of small classes in comparison to larger classes. Taking the individual variation in effects into consideration, we cannot rule out the possibility that small classes may be counterproductive for some students. It is therefore crucial to know more about the relationship between class size and achievement and how it influences what teachers and students do in the classroom in order to determine where money is best allocated.