This three-manuscript dissertation used a rapid PDSA to improve teacher efficacy concerning designing and teaching an unleveled 9th grade science class. Leveling and tracking can lead to inequitable outcomes and experiences for minoritized students. However, designing and implementing effective heterogeneous, unleveled classes that meet the needs of all students can be difficult. Teacher efficacy is an important component to the success of such courses and student achievement within the course. Therefore, improving teacher efficacy was key to creating an effective unleveled course that offered an equitable experience to all students. Manuscript 1 of this dissertation explores the negative experiences of one minoritized student group, African American/Black students, both in American Public Schools and the context of a large suburban high school in Massachusetts. Relevant literature is reviewed and framed within Bell (2013) and the Chinook Foundation (2010)'s Four I's of Oppression (Ideological, Institutional, Interpersonal, and Internalized). Manuscript 2 is a summary mixed methods study which measures the impact of a single professional development training focusing on Universal Design for Learning (UDL) Representation Principles on teacher efficacy. Seven teachers participated in the study. A 4.47% improvement is observed on the Science Teacher Efficacy Belief Instrument (STEBI) B for in-service science teachers, and a 13.75% improvement on the CP-related efficacy questions (Enochs & Riggs, 1990). Manuscript 3 proposes recommendations for organizational change and further research. Ultimately, the study finds that professional development is successful in improving efficacy, both in general and specific to creating materials for and implementing an unleveled science class. [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.]