Should you compete or cooperate with your classmates?

This paper presents empirical evidence from the Programme for International Student Assessment 2003 survey on the role of students' attitudes towards competition and cooperation in mathematical literacy achievement. While individual competitive attitudes are positively correlated with test scores, the reverse occurs when considering the aggregation of individual attitudes. Similarly, while individual cooperative attitudes exhibit a negative correlation with test scores, the opposite is true in the aggregate. We provide an interpretation of this ‘fallacy of composition’ based on public good production and incentives to free riding, which is prevented by social norms held valid in a small or homogenous group.