School is an environment where children and adolescents spend most of their time during the day. The environment is characterized by a sedentary culture necessary for academic learning. In this article, I present research evidence showing the effects of four physical activity opportunities in this environment: school athletics, recess, classroom physical activity breaks, and physical education. Based on an analysis of research evidence on the four opportunities, I propose that the efforts to promote the opportunities should be coordinated into a concerted action to integrate a physical activity-friendly culture in the sedentary environment. Using an example of China's whole-school physical activity promotion strategy, I identify four areas for us to continue to work on: legislature-based policies, physical education as core content, creation and maintenance of physical activity traditions in schools, and integration of physical activity-friendly culture into the sedentary school environment.