Purpose: The aim was to assess how two contextual variables, number of students per class and in-class global cooperation, affect students' academic performance in physical education. Method: Multilevel analysis was performed given the data's hierarchical nature (L1 = 1,185 participants and L2 = 64 classrooms), including regression analysis to assess how the contextual variables at the classroom level affected students' grades. Results: Results showed that the differences observed between classrooms in students' academic performance can be attributed largely to the perceived in-class global cooperation and not to the number of students per class. Group processing, promotive interaction, and individual accountability were the strongest predictors because these cooperative learning essential elements showed significant differences between classrooms. Discussion/Conclusion: Academic performance in physical education is not only determined by personal factors but also by contextual factors like perceived in-class cooperation. Group processing, promotive interaction, and individual accountability can be considered the most relevant critical features. Cooperative learning contexts are not easy to build, and depending on how successfully they are constructed, the outcomes can be very different.