The main aim of this study was to analyze the relationship between the amount of physical activity and academic performance in 3rd-year secondary education students. The sample was taken from three secondary schools in the area of Barcelona. 284 students (158 girls, 126 boys) with an average age of 14.7 yr. participated. The International Physical Activity Questionnaire was used by students to self-report their amount of physical activity. Students’ academic records were obtained for comparisons. Results showed that there was a linear relationship between academic performance and physical activity; nevertheless, there was a trend to stronger correlation when modeling the relationship between these variables with a quadratic equation. Further research should focus on whether academic performance and physical activity might be better explained with a second-order equation.