In this ethnographic study conducted in two classrooms in Norway, grade nine (14-year-olds) in lower secondary school and the first year (16-year-olds) of upper secondary school, attention is drawn to how classroom culture is constituted through relationships between students. Through processes of power, dominance, hegemony and marginalisation, classroom culture forms the conditions for a learning environment, and has different opportunities, dilemmas and costs for the students. As classroom culture is negotiated in contextual and relational processes, classroom culture and ways of performing masculinities and femininities vary in the different classrooms, even within the same school. This article explores two classroom cultures, a "rule-breaking" classroom culture and a classroom culture in which the fear of being labelled a "nerd" dominates, to show how boys and girls use different solutions to balance the development of their identity as youths (the youth project) and the acquisition of academic competence and skills (the qualifications project).