During adolescence, socialization of gender role attitudes (GRA) shifts from parents to peers, friends, and classmates; thus, it takes place primarily in the school context. Accordingly, previous studies identified school-related factors associated to adolescents' GRA. However, little is known about the relative importance of these factors as well as about the factors' differences between females' and males' GRA. This study investigates the relevance of several school factors on adolescents' GRA and gender differences. Using data from the German National Educational Panel Study (N = 10,866), the results show that attending a higher educational school type, higher classmates' socio-economic background, lower proportion of female classmates, and more egalitarian classmates' GRA are related to more individual egalitarian GRA. Furthermore, the relation between classmates' GRA and individual GRA is more pronounced for males than females. The study further discusses starting points for possible interventions.