Introduction: Although evidence-based interventions to prevent childhood obesity in school settings exist, few studies have identified factors that enhance school districts’ capacity to undertake such efforts. We describe the implementation of a school-based intervention using classroom lessons based on existing “Eat Well and Keep Moving” and “Planet Health” behavior change interventions and schoolwide activities to target 5,144 children in 4th through 7th grade in 2 low-income school districts. Methods: The intervention was part of the Massachusetts Childhood Obesity Research Demonstration (MA-CORD) project, a multisector community-based intervention implemented from 2012 through 2014. Using mixed methods, we operationalized key implementa...