The lack of physical activity in children has become a serious problem in our society in recent years. Physical inactivity is considered a risk factor for developing obesity and diseases such as diabetes (Morales et al., 2011). Apart from the physical benefits that physical activity bestows, some believe that cognition improves with physical activity, including benefits in the learning process. Aerobic fitness, in particular, appears to be related to academic performance (Guillamón, Canto, & Carrillo López, 2019). In fact, some studies report that higher level of aerobic performance is related to a higher efficiency in cognitive tasks that require optimal attentional control (Pontifex et al., 2011). Other studies show that interventions based on improving aerobic capacity may have positive effects on children’s academic achievements (de Bruijn, Hartman, Kostons, Visscher, & Bosker, 2018). While numerous studies have analyzed the relationship between academic performance and sportive habits, there is a lack of quantitative data on the relationship between aerobic capacity and academic performance in specific school subjects. The aim of the present study is to analyze the relationship between aerobic capacity and performance across different academic subjects in a sample of Spanish school children.