Information about state and local education policies regarding sexually transmitted infections, including human immunodeficiency virus, and unintended pregnancy prevention is available, yet less is known about school-level implementation of such policies. We examine trends in the percentage of US secondary schools teaching sexual and reproductive health (SRH) topics in a required course in Grades 6-8 and 9-12, including healthy relationships, sexual abstinence, condoms and condoms with other contraceptive methods. We analyze representative data from 38 states across six cycles of School Health Profiles (2008-18) assessed through self-administered questionnaires completed by lead health teachers. Logistic regression models examined linear trends in the percentages of schools teaching topics for Grades 6-8 and 9-12, separately. Trends were calculated for states having representative data for at least three cycles, including 2018. During 2008-18, it was more common to have increases in teaching how to obtain condoms, correct condom use and use condoms with other contraceptive methods in Grades 6-12 than decreases. More states showed decreases in teaching abstinence in Grades 6-12 than increases. Most states had no change in teaching SRH topics across grades. Findings suggest some improvement in school-based SRH education, yet efforts are needed to improve comprehensive, developmentally appropriate content.