High stakes testing is an increasingly powerful force in education with curricular decisions as one of the many factors influenced by this trend. A large number of districts and school leaders feel an increase in curriculum time for tested areas is the answer to America's academic shortcomings. The increase in instructional time for tested areas,…

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.…