Social participation means taking a full and active role in school life, being a valued and integral member of the school community. The purpose of this study was to examine pupils’ experiences of social participation and their active roles in Finnish primary schools. The intention was to find out in what ways primary school pupils’ (n = 3,760) personal experiences of pupil–pupil (PP) and pupil–teacher (PT) interaction vary between genders and across age groups in small and large schools. Pupils’ experiences were examined with questions concerning the active participation of the child and the participatory role of the teacher. The results show that pupils’ experiences vary, and there are differences between schools in terms of pupils’ social participation.