School-based adolescent sexual health education in the United States has long served as a means of combating emotional and physical threats to the well-being of youth. However, this sex education has since its inception marginalized the experiences and health concerns of lesbian, gay, and bisexual (LGB) students and contributed to school environments frequently hostile toward sexual minority groups. Growing concern for the welfare and educational experiences of sexual minorities suggests the need to improve school-based support for LGB students. This article explores this challenge by examining the relationship between sex education and sexual minorities. Through a review of the history of adolescent sexuality and sex education, and continuing barriers to support for LGB students, this article reveals how marginalization of LGB groups has manifested within schools and argues improving education with regards to LGB groups is necessary to develop equitable and safe educational environments. Suggestions for improving support of sexual minorities in schools and sex education are discussed.