Project Summary/Abstract Almost a third of children and adolescents in the US are overweight or obese. Childhood obesity has been shown to track into adulthood and increase the risk of other cardio-metabolic risk factors and diseases. While obesity is largely prevalent across the US, there are consistent disparities in its burden by socioeconomic status and race/ethnicity. Despite continued research on ways to curb the obesity epidemic, little progress has been made in reducing its burden. Schools are often seen as an ideal target for obesity prevention efforts and health equity promotion because of their ability to reach all children regardless of parental education or household level barriers. School characteristics, such as climate and environment, also play a role in overall educational attainment, a well-established risk factor for adult health, and have been associated with health behaviors such as diet and physical activity. However, disparities in factors such as educational attainment, academic achievement, and school quality exist along similar sociodemographic gradients as obesity and its related health behaviors. Fundamental structural changes to school environments and policies to promote equity across schools may represent a way to address disparities in childhood obesity while also improving social conditions for children. However, very few epidemiologic studies have examined the roles of school characteristics as they relates to childhood health, and there are no consistent indicators used for research. The overarching goal of this project is to assess the role of school characteristics in childhood weight status, physical activity, and the effectiveness of a school level physical activity intervention. Aim 1 will estimate the association between school characteristics and trajectories of BMI and in a nationally representative sample of US elementary school-aged children. Aim 2 will determine if, relative to individual and community level factors, school-level characteristics explain heterogeneity in BMI and physical activity among children attending elementary schools in Georgia. Aim 3 will determine if school characteristics modify the effectiveness of an evidence-based physical activity intervention implemented in elementary schools in Georgia. The results of this dissertation may inform the implementation of school-based obesity prevention programs, and provide evidence to school and education policy-makers.