Using data from the third School Nutrition Dietary Assessment Study, this study estimates the association between school food environments and practices and children’s likelihood for obesity. (Obesity was defined as having a body mass index greater than the 95th percentile for their age.) The national study involved more than 2,200 children in 287 schools. The findings suggest that offering low-nutrient, energy-dense foods (french fries, desserts) more than once a week (in elementary schools) or in vending machines (in middle schools) is associated with a higher likelihood of obesity.