Background: Deficient vocabulary is a frequently reported symptom of developmental language impairment, but the nature of the deficit and its developmental course are not well documented. Aims: To describe the nature of the deficit in terms of breadth and depth of vocabulary knowledge and to determine whether the nature and the extent of the…

Background: Cluster-randomized experiments that assign intact groups such as schools or school districts to treatment conditions are increasingly common in educational research. Such experiments are inherently multilevel designs whose sensitivity (statistical power and precision of estimates) depends on the variance decomposition across levels.…

"Success for All" (SFA) is one of the best known and thoroughly evaluated school reform models. Further evaluation of the initiative is especially important for two reasons. First, the program model has continued to evolve over time, with a greater emphasis placed on the use of engaging technology in the classroom and on the deployment…