The reasons for peer education's ascendance as a core pedagogy in sex education are as much historical as they are reasonable or ethical. This article traces the history of peer-led sex education from the 1970s to the 1990s against the backdrop of New York City's financial ruin, social unrest, and a public health crisis. Starting with an analysis of the Student Coalition for Relevant Sex Education's Peer Information Project, founded in 1974, it investigates the application of new pedagogical techniques, the interplay between pedagogy and bureaucracy, and the transformation of school culture. Peer education thrived when educators and activists agreed that young people were more likely to accept advice from other young people, a reasonable contention that was nonetheless underassessed. Yet peer education's least intriguing attribute proved to be its most important characteristic: it could be quickly and inexpensively enacted. When HIV/AIDS began to decimate New York City's adolescent population, and the Board of Education proved slow and contradictory in its actions, the city turned to peer education, henceforth coupling the concepts of sex education and peer education.