We examined associations of teacher-perceived student temperament and educational competence with school achievement, and how these associations were modified by students' gender and teachers' gender and age. Participants were 1063 Finnish ninth-graders (534 boys) and their 29 Mother Language teachers (all female) and 43 Mathematics teachers (17 male) from a population-based sample. All temperament and educational competence traits were associated with both grades, but more clearly with Mathematics. Boys received systematically lower Mother Language grades but higher Mathematics grades than girls. Teacher gender had no effect on school grades, while teacher age had an effect only on Mother Language.