How does institutionalized heterosexism manifest itself in Icelandic upper secondary schools and how do lesbian, gay, bisexual, and transgender (LGBT) students respond to these manifestations? In addressing these questions, interviews were conducted with six current and former LGBT upper secondary school students, using queer theory and thematic analysis. It is argued that institutionalized heterosexism prevails in the structure and culture of the schools under investigation, although to varying degrees. LGBT youth experienced institutionalized heterosexism daily in their dealings with faculty and fellow students. The LGBT students who were interviewed responded to the oppressive nature of institutionalized heterosexism in various ways. Some tried to resist the system actively while others did so more subtly. In general, their stories can be interpreted as having destabilizing effects on the heterosexual system.