Culturally proficient leaders model cultural competence for the entire school community. They create an environment where students from diverse backgrounds feel valued, respected, and safe. When students feel a sense of belonging and affirmation, they are more likely to engage in their learning and perform better academically. Hence, this phenomenological qualitative study examined school leaders' culturally responsive leadership efficacy as it relates to the promotion of culturally relevant professional learning communities. The goal of this study was to look closely at the school leaders' experience as a culturally responsive leader and investigate how that efficacy builds sustained culturally relevant professional development among schools where they have 50% or more of their students from marginalized communities. Exploring the school leader's definition of equity, the strategies they used to implement culturally relevant professional learning, and their perception of teacher effectiveness of culturally relevant pedagogical practices through the ZOOM virtual conferring platform and an interview protocol which included 10 semi-structured questions, helped examine the school leaders' experience with supporting teachers in culturally relevant pedagogical practices. Asking school principals from the Northeast region of the United States, excluding New York City, who lead schools where more than half of their students are from marginalized backgrounds helped to assess whether or not a principal's self-proclaimed culturally responsive leadership efficacy could lead to a sustained culturally relevant professional learning community that removed the barriers that hinder marginalized students. The results revealed that all principals had a similar definition of equity. They believed all children should have what they need to succeed in education, but lacked the necessary training and professional development to effectively integrate culturally relevant pedagogy to systematically implement best practices for marginalized students in their schools. Principals used professional development to supplant sources of inequity such as curriculum and teacher mindset. However, the deficit lens mindset by teachers and the lack of professional development time to devote to Culturally Relevant Pedagogy (CRP) hinders it from being implemented with fidelity. The principals in this study declared their advocacy for their students and expressed their desire to be equipped with better resources and tools to fight the inequities that continue to plague students from marginalized backgrounds, such as a "one-size-fit-all" curriculum, and teachers who are ill-prepared to teach the diverse needs of the students. In addition to the call to action by Muhammad Khalifa, this study has heightened the training school leaders require to cultivate, develop, and implement professional development to provide teachers with tools needed to teach all students, regardless of cultural backgrounds. Resulting in the barriers that continue to plague the educational system for students from marginalized communities being removed. This study also recommends that culturally responsive practices should become part of the principals' evaluation tool. Finally, this study further recommends that school leaders use a research-based professional development tool that focuses on culturally responsive practices to assess their culturally relevant learning community. In summary, a school leader's cultural proficient leadership efficacy is of paramount importance in improving the academic achievement for students of marginalized backgrounds. A school leaders' commitment to equity, cultural relevance, teacher development, data-driven decision-making, and community engagement can have a transformative impact on the educational experiences and outcomes of these 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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]