Schools are an important setting for addressing childhood obesity. More than 54 million U.S. children attend school, and 8.4 million youth are in after-school programs located in schools, parks, and recreational centers. A substantial portion of school-aged children’s daily food and caloric intake occurs within the school and after-school environment. The aim of the research in this area is to understand how school and after-school food policies and environments can help prevent childhood obesity.