Not many interventions are available to improve the school climate for lesbian, gay, and bisexual (LGB) youth in prevocational secondary education. In four schools with different student populations, this study examined the impact of a newly designed peer-educator intervention on attitudes towards lesbian women and gay men and on the class climate for LGB youth. The possibility of disclosing a non-heterosexual orientation in school was also assessed, using a pretest, post-test one-group design. We found limited and marginal effects of the intervention. Some evidence that the intervention was better tailored to the needs of female students is discussed.