The present study was designed to explore the association between preschool academic skills and Grade 3 achievement among a sample of ethnically diverse children from low-income families. Data were collected from a sample of 1,442 low-income, ethnically diverse children in preschool and associated with Grade 3 achievement in reading and…

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.…