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.…

The "No Child Left Behind" (NCLB) Act of 2001, Public Law 107-110 (U.S. Congress), was passed by Congress in response to perceived failure of the public school system to effectively educate students, particularly disadvantaged students in the United States. The relationship of NCLB school choice to student achievement has not been…