International health and education sectors alike readily support the argument that healthy young people who attend school tend to learn better, and a good education influences the development of a healthier population. Such sentiments recognize the interaction between schools and young people, and the overall experience of attending school as providing unique opportunities for health promotion. Yet many believe that such programs have never been fully embraced. In this paper we explore tensions operating at the health-education interface and the complex nexus of principles and practices within which educators and health professionals mobilize school-based health-promotion initiatives. In so doing, we draw on the case of health literacy to demonstrate the usefulness of an explicit interrogation of the theoretical lineages underpinning particular strategies as a means of mediating these tensions. More specifically, we provide insight into the principles and practices underpinning educators' approaches to evaluation, and pose some implications for school-based health education and promotion.