Establishing Language Benchmarks for Children With Typically Developing Language and Children With Language Impairment.

Purpose: Practitioners, researchers, and policymakers (i.e., stakeholders) have vested interests in children's language growth yet currently do not have empirically driven methods for measuring such outcomes. The present study established language benchmarks for children with typically developing language (TDL) and children with language impairment (LI) from 3 to 9 years of age. Method: Effect sizes for grammar, vocabulary, and overall language were calculated for children with TDL (n = 20,018) using raw score means and standard deviations from 8 norm-referenced measures of language. Effect sizes for children with LI were calculated using fall and spring norm-referenced language measures for 497 children with LI receiving business-as-usual therapy in the public schools. Results: Considerable variability was found in expected change across both samples of children over time, with preschoolers exhibiting larger effect sizes (d = 0.82 and 0.70, respectively) compared with school-age children (d = 0.49 and 0.55, respectively). Conclusions: This study provides a first step toward establishing empirically based language benchmarks for children. These data offer stakeholders an initial tool for setting goals based on expected growth (practitioners), making informed decisions on language-based curricula (policymakers), and measuring effectiveness of intervention research (researchers).