Objectives: An increasing number of nutrition policies have been implemented in Ontario schools as part of a concerted effort to address students' well-being. This article explores understandings of biological differences in nutrition requirements between young men and women and the extent to which these differences are (re)produced in social eating behaviours and food pedagogies. Setting: A suburban school (grades 9-12) located in the Greater Toronto-Hamilton Area in Ontario, Canada. Method: Critical policy analysis combined with 13 focus groups of students (13-18 years old) in one Ontario school. A biopedagogical lens was used to analyse how young people develop and deploy their own reasoning and question the messages they receive about expected behaviour. Results: Focus group discussions suggest that dominant discourses and constructions about sex/gender are reproduced within the school environment, which has implications for the effectiveness of nutrition policies in schools. Furthermore, differences between young men and women's eating behaviours were found to be contradictory to biopedagogical instructions from educational institutions and governmental agencies. For some young people, the pedagogical messages received are limited in their effectiveness because young people have not been convinced that it is worth risking their social status or because their content is contrary to messages received from media or their peers. Conclusion: Incorporating student voice in the creation of educational policy will assist health educators and school officials to understand sex/gender influences on the behaviour of students in terms of financial considerations, peer influence and social image. Optimising student voice to understand how they themselves may contribute to the implementation of policies will in turn increase the policies' effectiveness.