RESUMEN
The program code developed by others is appropriately cited in the text and listed in the references section. The raw and processed data on which study conclusions are based are not available. The statistical syntax needed to reproduce analyses in the article is available upon request. The methods section provides references for the materials described therein. We report how we determined our sample size, all data exclusions, all manipulations, and all measures in the study, and we follow APA Style Journal Article Reporting Standards. This study's design, hypotheses, and data analytic plan were not pre-registered. Prior research supports the need for elementary-aged students with reading difficulties (RD) to receive explicit systematic small group evidence-based reading instruction. Yet for many students, simply receiving an evidence-based reading instruction in a small group setting is insufficient to reach the progress milestones needed to meet grade level reading standards. The current study examined whether: (1) elementary school students with RD constitute a homogeneous or heterogeneous groups when considering their basic language and cognitive skills (using a latent profile analysis), and (2) if latent profiles are predictive of response to reading comprehension instruction (using a mixed modeling approach). The sample consisted of 335 students, including students with RD and typical students (n = 57). The results revealed heterogeneity within students with RD - there were two distinct profiles, with one having higher basic language (reading fluency and decoding) and cognitive (verbal domain productivity, cognitive flexibility, working memory) skills and lower attention skills, and the other having stronger attention skills and lower basic language and cognitive skills. The findings also suggested that latent profiles were predictive of response to reading comprehension instruction. Our results provide a convincing argument for leading the field in the direction of developing customized interventions. It is conceivable, but remains to be further examined, that researchers and educators could potentially improve reading outcomes through providing a customized reading intervention to a student based on their cognitive-language profile.