This phenomenological study investigated the impact of culturally proficient leadership behaviors on culturally diverse school populations and sought to identify culturally responsive practices used by culturally proficient school leaders. The research was conducted in a suburban Title I school district in California with a diverse student population. Qualitative methods were used to collect data from school leaders who had participated in cultural proficiency professional development.The findings revealed that culturally proficient leadership behaviors positively impacted culturally diverse school populations, and culturally responsive practices included building relationships, understanding cultural differences, and being intentional in communication and decision-making. Characteristics shared by culturally-responsive leaders serving culturally diverse populations included being adaptable, empathetic, and committed to equity and inclusion. Participating in cultural proficiency professional development helped school leaders develop a better understanding of cultural responsiveness and how to apply it in their leadership practices. The study's findings highlight the importance of implementing culturally proficient leadership practices in diverse school settings and offer valuable insights into the challenges and opportunities associated with cultural proficiency development. The study contributes to the educational community's understanding of culturally responsive and effective leadership practices. The study calls attention to the crucial need for school leaders to build cultural proficiency within themselves and their staff and implement culturally responsive practices to meet the needs of diverse student populations. [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.]