Gay-straight alliance (GSA) clubs may positively affect mental health for lesbian, gay, bisexual, transgender, and questioning (LGBT) students, but little research has studied schools that primarily enroll LGBT students. Guided by neofunctional and sexual stigma theory, the purpose of this study was to determine if graduates of LGBT high schools have better mental health than LGBT and heterosexual graduates of mainstream high schools. A snow ball sample, of 183 graduates of high schools in the United States and 95 graduates from high schools in other countries, 80% who identified as LGBT, completed an online survey consisting of 5 short mental health assessments, measuring anxiety, depression, self-esteem, internalized homophobia, and life satisfaction. Including demographic variables as covariates, ANCOVA was used to test for significant difference in the mental health of former students who have attended high schools with GSAs (GSA+) compared with graduates of high schools without GSAs (GSA-). Research results found that U.S. graduates of GSA+ high schools had significantly higher self-esteem (p = .034) and life satisfaction (p = .026) than U.S. graduates of GSA- high schools. Graduates of non U.S. GSA+ high schools had significantly lower levels of depression (p =.016) than graduates of U.S. GSA- high schools. Students who identified as gender conforming had significantly higher levels of self-esteem (p =.004) and significantly lower levels of depression (p = .000) than students identifying as nongender conforming. The social change implications of these findings include urging school administrations across the country to support GSAs as they may improve the mental health of students who identify as LGBT or nongender conforming.