Part of the broader Evaluation of Adolescent Pregnancy Prevention Approaches (PPA), this study evaluated the impacts of a Chicago Public School demonstration project to support the implementation of HealthTeacher, a nationally popular and affordable online K–12 health education program, in a select number of 7th-grade classrooms. Although HealthTeacher had substantial impacts on students' exposure to information on reproductive health, contraception, and sexually transmitted diseases, the study found little evidence that the program changed youths' knowledge of these topics. The program did not affect their confidence in their ability to refuse sexual contact from someone they knew, their attitudes or intentions toward sexual activity or contraception, or actual sexual activity.