Physical activity (PA) policies have the potential to ensure adequate opportunities for children to develop PA behaviors for a lifetime. Examples include mandating that schools provide recess and physical education for a specified amount of time per week; ensuring that physical education teachers are licensed; providing activity breaks in academic classrooms; and mandating the implementation of policies at federal, state, and local levels. Collectively, these policies help to promote and support Comprehensive School Physical Activity Programs (CSPAP). However, there is little guidance on how PA policies can be implemented at the school and district level, limiting their impact on promoting student behaviors. Therefore, the purpose of this paper is to provide an overview of research conducted on CSPAP policy development, adoption, and implementation and how best to support local implementation efforts in schools to increase PA and its impact on children's health. We provide pragmatic recommendations for how school and district leadership can use implementation science principles to assess current policy implementation and advocate for more comprehensive PA policies which support systems change.