This review examines possible relationships between academic performance and participation in sports, physical education, and other forms of physical activity. Recent fundamental research has reignited interest in the effects of physical activity on cognitive processes. Experimental studies of potential mediating variables point to physiological influences such as greater arousal and an increased secretion of neurotrophins and psychosocial influences such as increased self-esteem and connectedness to schools. In the specific case of sports, experimental studies are limited to demonstrations of greater attention and acute gains of mental performance immediately following such activity. Several quasi-experimental studies of other types of physical activity have been completed, mainly in primary school students; these have found no decrease in academic performance despite a curtailing of the time allocated to the teaching of academic subjects. Indeed, in some cases, experimental students undertaking more physical activity have out-performed control students. Many investigators have looked at cross-sectional associations between participation in sport or other forms of physical activity and academic performance. Despite difficulties in allowing for confounding variables, particularly socioeconomic status, the overall conclusion has been of a weak positive association. From the practical point of view, it can be concluded that the physical activity needed for healthy child development can be incorporated into the school curriculum without detriment to academic achievement.