Educators and policymakers have set a goal that all students graduate from high school ready for college and careers. A substantial body of research supports the idea that the path to college and career readiness begins well before middle and high school. In an earlier policy report, ACT examined the percentage of academically far off track…

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.…