Overweight and obesity are major health concerns for young people. Schools are particularly promising environments for preventing and treating obesity. The Institutes of Medicine recommends 60 minutes per day of physical activity for children and youth, including at least 30 minutes at school. Yet the amount of moderate to vigorous physical exercise children and youth receive at school falls far short of these recommendations. Several intervention programs are supported by well-controlled studies. These effective programs include Planet Health, the Stanford Adolescent Heart Health Program, Dance for Health, Cardiovascular Health in Children, and the Middle School Physical Activity and Nutrition. Unfortunately, the many methodological shortcomings and inconsistencies in the obesity prevention literature make it difficult to draw clear conclusions about effective program components. Specific resources and recommendations are included to guide school psychologists in improving their schools' climate for health. © 2009 Wiley Periodicals, Inc.