The past two decades has seen widespread academic and public concern about boys' academic achievement and the emergence of discourses that identify girls as academic 'winners' in the primary classroom; however, this article aims to problematise these trends. Drawing on ethnographic research carried out in a primary school classroom in London, this article draws attention to 'boysplaining,' a set of behaviours carried out by certain boys which constituted a form of hegemonic masculinity in this classroom. Boysplaining, a younger version of mansplaining, manifested both verbally and physically, and appears to affect how girls navigate the classroom. This research indicates how boysplaining disadvantages girls, raising questions about the extent to which girls are 'winning' in primary school classrooms today. The article calls for further research on boysplaining in other classrooms, in particular to examine the academic, social and emotional consequences of these behaviours on girls and non-hegemonic boys.