Today, obesity is one of the most critical health concerns for children in the United States. Nearly one-third of children and teens are overweight or obese--and physical inactivity is a leading contributor to the epidemic. Regrettably, as a result of budget cuts and pressure to ensure students perform well on academic tests, physical education (PE) has been significantly reduced, and in some cases completely eliminated in schools across the country. However, the available evidence shows that children who are physically active and fit tend to perform better in the classroom and that daily physical education does not adversely affect academic performance. School physical education programs, recess, classroom physical activity, and extracurricular physical activities cannot singlehandedly reverse the current childhood obesity epidemic. However, more than 50 million students spend a significant portion of their daily lives in school; so this social context is surely one of the most powerful institutions shaping the next generation of youth. If district or local school policies are not put in place to ensure that children engage in physical activity during the school day, their risk of obesity will continue to rise. (Contains 10 endnotes.)