Due in part to testing pressures, for years the science subject has taken a back seat to reading and math. And though topics like volcanos and time travel have the potential to get kids' attention, science's status as a curricular stepchild typically translates into dull textbooks and little budget for experiments or supplies. The tide is…

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.…