Over 55 million children and adolescents attend elementary and secondary schools in the United States, 89 percent in public schools. These students spend approximately 1000 hours each year in schools across the country, for which local, state, and federal governments spend over $550 billion (National Center for Education Statistics [NCES] 2008). Education is an intensive and costly enterprise. It also has the potential to dramatically improve opportunities for students. In the United States, estimates of the return to an additional year of schooling are in the neighborhood of 10 percent, depending on the data and method (Card 1999). Educational attainment is also associated with differences in individual health, incarceration, and dependence on public assistance (Belfield and Levin 2007). While schooling improves children’s lifetime opportunities, the debate on how to use scarce time and resources to maximize outcomes while in school is not settled.