Santa Ana, California has the highest teenage birth rate in Orange County, USA, at 28.2 per 1,000 women aged 15-19 as compared to 12.0 per 1000 women of similar age elsewhere in the county. In the light of this disparity, University of California Irvine medical students surveyed a convenience sample of 9th grade students (aged 14-15 years) in Santa Ana to assess the efficacy of a medical student-led sex education programme. Nine 50-minute sex education lessons were conducted over a 2-week period, with pre- and post-tests to evaluate knowledge retention. A total of 301 pre-tests and 295 post-tests were collected. Of 27 multiple choice questions, the mean number of correct questions on the pre-test was 11.3 (± 4.2) compared to 14.1 (± 5.0) questions on the post-test. There was significant improvement in scores following the implementation of the curriculum (p < 0.001). Overall, findings demonstrate that medical students can effectively teach a sex education curriculum. The study serves as a potential model for sex education in geographic areas that exhibit disparities in teenage birth rates.