In October 2021, California passed Assembly Bill No. 101, making it the first state in the nation to add ethnic studies as a high school graduation requirement. Ethnic studies programs provide students with a comprehensive understanding of diverse cultures, histories, and perspectives, while fostering inclusive learning environments and empowering students to see themselves as valuable members of the community. However, the success of such programs relies heavily on the expertise and preparedness of educators developing and instructing these courses. As an interdisciplinary field without course-specific state credentialing or certification requirements, effectively training educators tasked with teaching ethnic studies is critical in developing a transformative learning experience for California high school students. This dissertation investigates professional development and ongoing systems of support for ethnic studies teachers at the high school level and proposes strategies to enhance educators' effectiveness and confidence in teaching ethnic studies. As such, nine ethnic studies educators from the Northern Valley Unified School District (pseudonym) shared their experiences and perspectives in developing and implementing a required ethnic studies course. Based on the findings presented in this study, participants advocate for job-embedded collaboration to develop content and share best practices. In addition, participant responses highlight the importance of student-centered ethnic studies pedagogy and the need to develop and sustain reflective ethnic studies curriculum. By equipping teachers with the necessary training, resources, and support, ethnic studies educators can cultivate a classroom environment that nurtures cultural understanding, critical thinking, and social consciousness among students. [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.]