This critical case study addressed how the achievement gap reflects the culture gap between teachers and historically underrepresented students. This study allows educators to consider how attitudes on culture and diversity impact student achievement. It makes visible existing teacher and student relationships in a rural school system through the lens of cultural proficiency. Guided by a conceptual framework outlining culturally proficient practices, the overarching research question asked teachers about their perception of student achievement relative to the lens of cultural proficiency. Thirty-four secondary teachers with varying years of teaching experience were purposefully selected. They completed an online inventory via Survey Monkey which consisted of 4 self-assessment rubrics examining culturally proficient behaviors and dispositions relative to elements along the cultural proficiency continuum. Additionally, a sample of 8 teachers from the initial group participated in individual interviews responding to a set of related questions. The data obtained from the interviews were coded using pre-established categories and patterns based on expected themes and recurring ideas, and analyzed by forming patterns to identify trends, clusters, outliers, or gaps. The study's key finding was the school system's need for a meaningful, sustained professional development beyond content knowledge and pedagogical practices in order to create a more culturally proficient teaching faculty. The study contributes to social change by addressing the impact of ethnocentric attitudes on cultural diversity and ultimately student achievement in the hopes of aiding teachers in the construction of a learning culture free of educational and social inequities. [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.]