This study investigated children and adolescents' school performance over time focusing on two variables that may influence it: developmental context and gender. The sample comprised 627 participants (M[subscript age]?=?11.13, SD?=?1.8), 51% of them female, from grade one to eight, living either with family (n?=?474) or in care institutions (n?=?153). Participants answered individually the "Teste de Desempenho Escolar" (School Performance Test) and the Structured PRONEX Interview. Findings indicated a main effect of time on school performance (i.e., writing, reading and arithmetic). Furthermore this main effect was further qualified by a time and developmental context interaction and by a time and gender interaction. Interactions revealed that the participants from care institutions attained more significant increases in writing and reading than participants living within a family context; and that girls attained more significant increases in writing than boys. Therefore, school performance progress appears as affected by developmental contexts and gender. The findings reveal how school performance needs to be observed as a multidimensional variable, affected by individual characteristics but also by external ones.