Background: Schools are a setting in which students learn about the importance of lifelong physical activity (PA). Best practice guidelines indicate that schools should provide students with adequate physical education (PE) minutes and opportunities to engage in PA throughout the school day. Methods: Data from the nationally representative School Nutrition and Meal Cost Study in 2014–2015 were utilized to assess PA practices (including PE) at 412 public elementary schools. These data were linked to state- and district-level policy data from the National Wellness Policy Study to examine the relationships between state law and school district policies and school practices. Results: Just over half of the schools were in a state with a policy regarding PE minutes. The comprehensiveness and strength of PA policies were higher at the district level than the state level, but were still low overall. Comprehensiveness of PA policies at the state level, but not at the district level, was related to schools within those states that provide more PA practices. Conclusions: Existence of PE and PA policies at the state level appears to be an important predictor of school PA practices. Having more comprehensive policies at the state level may be an important facilitator of school implementation of comprehensive PA practices.