Differential codevelopment of vocabulary knowledge and reading comprehension for students with and without learning disabilities.

In this large-scale study of students from Title 1 schools (N = 14,773), we used multiple-group latent change score (LCS) modeling to investigate the developmental relations between vocabulary knowledge and reading comprehension in students with a school-identified learning disability (LD, n = 627) and typically developing students (n = 14,146). Students were tested for their vocabulary breadth and passage comprehension skills in Kindergarten through fourth grade. For typically developing students, there were bidirectional influences between their vocabulary knowledge and reading comprehension skills. There were no cross-lagged influences across constructs for students with an LD. We find evidence for a developmental delay, such that students with an LD had similar levels and gains in their vocabulary knowledge relative to typically developing students, but these students started much lower in their reading comprehension skills and did not catch up to their typically developing peers. We discuss the implications for children with learning disabilities and the development of their reading comprehension skills.