This paper offers an examination of gay-straight alliance (GSA) members' engagement with sex education, sexual health, and prejudice and discrimination in Canadian public high schools. It explores how five students' (four straight and one gay-identifying) participation in GSAs served as a springboard for learning about and challenging stereotypes; prejudice; and discrimination directed at lesbian, gay, bisexual, trans, and queer/questioning (LGBTQ) people. Queer theory provided the theoretical underpinnings of the study, offering a lens through which to examine the heteronormative underpinnings of education, and a means to interpret how homophobic discourses circulate in school and society. Empirical data were obtained via observational notes from visits to nine GSAs and semi-structured interviews with the five GSA members. Findings suggest that straight allies can use their heterosexual privilege to address LGBTQ issues with their peers. Through GSA involvement, participants learned to interrogate and combat stereotypes about LGBTQ people and HIV-related myths, as well as to engage in queer discussion and political action.