The purpose of this quantitative retrospective study was to understand the impact of prior exposure to sexual health education on middle and high school students' sexual health knowledge, self-efficacy, and intentions. The study analyzed a secondary dataset that included pre- and posttest results collected for program evaluation purposes by a leading provider of sexual health education in California from approximately 8,500 middle school and high school students. Of those participants, pretest and posttest results for 1,626 middle school students and 1,103 high school students were matched using self-generated identification codes. Middle school and high school cohorts were analyzed separately based on self-report of prior doses of sexual health education (0, 1, 2, and 3 or more prior doses) using one-way analysis of variance, paired t-tests, and chi-square tests for association. Results of this study suggest promising, though quite modest, impacts from prior exposure to sexual health education. There were minimal statistically significant differences between dosage groups in sexual health knowledge. There were statistically significant differences between dosage groups on self-efficacy-aligned survey items and on the single intention-related survey item. This study also exposed some counterintuitive dynamics with regard to self-efficacy and prior exposure, such that students without prior sexual health instruction may exhibit greater confidence in their ability to execute sexual health-promoting behaviors than participants who report one or two prior doses. Taken together, the results suggest that it may be important to look beyond the outcomes of a single intervention and understand how interventions may provide compound outcomes over time. There are important limitations to this study, including the use of self-reported prior exposure and the lack of validated survey items to measure the theorized constructs. Nonetheless, the results provide support for the integration of multiple doses of comprehensive, inclusive, age-appropriate sexual health education programming to more effectively incorporate sexual health education across the K-12 educational life cycle. This study also prompts important questions and potential opportunities to understand the nuances and intricacies of how dosage over time functions in sexual health education. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]