We investigated whether personality moderates group influence of classmates on academicachievement and whether these so-called contexteffects can be attributed to peer pressure. The sample consisted of 2498 students in their first year of Dutch secondary education. The data were analyzed by a two-level (students within classes) analysis, separately for boys (n = 1033, in 92 classes) and girls (n = 1465, in 119 classes). For both sexes, we found acontexteffect on Dutch language achievement but not on mathematics achievement. Emotional Stability appeared amoderator of this contexteffect but for girls only. The results suggest further that peer pressure is not a likely mechanism of group influence of classmates on academicachievement.