This research examines the impact of same-sex versus opposite-sex social comparisons on the perception of one's own abilities at school and subsequent reported marks and academic choices. During their final year, male and female high school students were asked to describe themselves either in comparison with boys in their class, in comparison with girls in their class or without any explicit social comparison (control group). The interaction effects of gender and comparison context on academic self concept, school marks and academic choices indicated that gender differences depend on the comparison context. Particularly, as predicted, gender differences disappeared in the same-sex social comparison condition, and even became inverted for the intended academic choices. Here, boys intended to choose more than girls Preparatory Courses for Higher Education (PCHE) in the opposite-sex social comparison condition, while girls more often chose a prestigious PCHE than boys in the same-sex social comparison condition. The theoretical, methodological and practical implications of these findings are discussed.