The Canadian education system is among the best in the world academically. In contrast, students' (children and youth) eating and activity levels are so poor that they have led to prevalence rates of overweight that are among the highest in the world. Given the enormous public health burden associated with poor nutrition and physical inactivity, Canada needs to address this health risk. Comprehensive school health (CSH) is a promising approach to promoting healthy eating and active living (HEAL). This article provides a review of CSH and discusses its four essential elements: 1) teaching and learning; 2) social and physical environments; 3) healthy school policy; and 4) partnerships and services. It also provides a common understanding of the implementation and broader benefits of CSH, which, in addition to health, include student learning and self-esteem. The article further discusses some complexities of a rigorous evaluation of CSH, which comprises proof of implementation, impact and positive outcome. Though such an evaluation has yet to be conducted, some studies did confirm successful implementation, and another study observed positive outcomes. Rigorous evaluation is urgently needed to provide a stronger evidence base of the benefits of CSH for learning, self-esteem and disease prevention. This evidence is essential to justify devoting more school time to promote HEAL and more resources to implement and support CSH to the benefit of both learning and health.