Physical inactivity is a serious public health problem that is associated with numerous preventable diseases. Public health concerns, particularly those related to the increased prevalence of overweight, obesity, and diabetes, call for schools to become proactive in the promotion of healthy, physically active lifestyles. This article begins by differentiating physical activity from associated concepts (e.g., physical education, physical fitness) and then summarizes the literature related to the importance of physical activity for children and the need for its promotion in elementary schools. We describe numerous opportunities for children to accrue physical activity in elementary schools (e.g., physical education classes, program integration with other subject areas, recess, extracurricular programs, and active transport to school) and provide recommendations for sound educational practice.