This article focuses on uncovering social inequality in non-curricular activities (NCAs) and looking at the impact these have on young people's school performance. Based on research conducted in Barcelona with 2,156 10th-graders, the authors investigate the association of participation in NCAs with academic outcomes in the context of social stratification. Their analysis of the data show how the choice of NCAs differs according to gender, immigrant background and family education level. Their findings also indicate that NCAs have an impact on academic performance, and that this effect is amplified when the family educational level variable is introduced. The largest impact of these activities occurs among students whose parents' highest level of education is compulsory education. If students in this social group do not participate in any of the NCAs, their grade point average is associated with the worst performance among young people in Barcelona. On the other hand, if they take part in sports or artistic activities at school, their grade point average is the highest in their social group. The article concludes with some recommendations for socio-political and educational intervention, at the level of schools and the educational community as well as at the policymaking level.