This article presents early evaluation data on the effectiveness of an ethics-based sex education program, the Sexual Ethics for a Caring Society Curriculum (SECS-C), which strives to develop adolescents' thinking about sex so that they might act ethically in relation to other people and reflect ethically upon sexual messages and events in the world around them. Unlike typical evidence-based curricula that measure prevention goals from a health perspective, effectiveness was measured in terms of attitude change. Seventy-nine 9th graders from 7 diverse classrooms at a charter school received 8 lessons from the curriculum. Pre and post measures assessed belief in rape myths (the Illinois Rape Myth Acceptance Scale) and bystanderism (the Bystander Attitude Scale, Revised (BAS-R)). The students showed improvements with regard to rape myth attitudes but not with regard to their beliefs in the likelihood of intervening in troublesome sexual situations.