STIs in youth in New Jersey is a growing concern. According to New Jersey' Public Health Data Resource (2020), the total number of STIs in youth from age 15-24 totals 19,698. The current STIs-related sex education programs vary widely in New Jersey in terms of scope, the accuracy of content, emphasis, and effectiveness (Thrive New Jersey Coalition, 2019). Therefore, students may have quite different levels of awareness on the prevention of STIs. The purpose of this qualitative collective case study was to explore the T (theta) (Stake, 1995) of the "why" and "how" of health educators' decisions in designing STI content and instructing students on the same. The study aims to understand how health educators' decision-making regarding the content and instruction of STIs causes dissimilarities among schools' sex education programs in New Jersey and how health educators' decisions about content and delivery directly impact the social issue of the increasing STIs incidence in youth. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]