Prior studies show a strong association between gay-straight alliances GSAs and the well-being and safety of sexual minority students at school. However, nearly all existing literature has relied on cross-sectional data. Using data from the first two panels of a multi-site longitudinal study on risk and protective factors for suicide among lesbian, gay, bisexual, and questioning LGBQ youth in three U. LGBQ students who had GSAs in their schools or were members of GSAs in the prior year showed no differences in psychological adjustment, but they reported perceptions of more school safety and less homophobic bullying in the following school year. Further, changes in GSA presence gaining a GSA and changes in participation from non-participation to participation were independently associated with stronger perceived safety in the subsequent school year. This study provides the first prospective evidence of the lasting positive role of GSAs for high school students, and documents that changes in GSA presence and participation are associated with safety at school.