Consistent with NIH priorities, our long-term objective is to reduce the rates and risk of childhood obesity via school-based nutrition and physical activity policies. We propose to monitor and evaluate how Connecticut's first-ranked School Wellness Policy, in the New Haven Public School district, is implemented and determine its impact on children's obesogenic behaviors, weight outcomes, and school performance. We will evaluate a strategy of implementation at 12 targeted schools using a randomized design. Focusing on targeted schools will enable a more rigorous evaluation of School Wellness Policy implementation, barriers/facilitators, and ultimately the behavioral and health impacts of school-based policies on childhood obesity. We propose a multi-level assessment of factors that may influence childhood obesity using the Ecological Model as a guiding framework.