A school district on a Native American reservation in the southwestern region of the U.S. decided to implement the Teacher Advancement Program (TAP) to improve teacher instructional effectiveness and student academic achievement. Although researchers have documented successes of the TAP in high-poverty urban school districts across the U.S., little is known regarding the TAP implementation in remote Native American cultural context schools. The purpose of this study was to investigate if the collaborative process of the TAP implementation changed the teachers' instructional practices. Using Vygotsky's social constructivism, which emphasizes that learning happens through interactions and cooperation of people in their environments, this qualitative case study investigated 9 teachers' perceptions of the TAP implementation using interview, walkthrough observation and document analysis at the schools. The research questions focused on teachers' perceptions of TAP elements, their experiences, changes in practices and the influence of the Native American setting. A qualitative data analysis software program and constant comparison method were used to manage and analyze the qualitative data. Findings indicated that positive collegial collaboration, teacher attitude, and instructional change were associated with the TAP implementation, teacher evaluation (most challenging experience), teacher professional growth, and student academic achievement growth (most rewarding experiences). A district professional development plan was created to build on the strength of the TAP collegial collaboration and to meet the rigorous demand of the new state College and Career Readiness standards. The change of teachers' working in isolation to collegial collaboration reflects a positive social change for continuous inquiry into both student and teacher learning.