The purpose of this study was to gather teacher and parent perceptions about a collective approach to PLCs and their impact on student achievement in Algebra 1, Algebra 2, and Geometry. This research, carried out as a single case study at a high school in West Tennessee, used a qualitative research method to identify which PLC structure, whether a collective approach or whole group, was more conducive to improving teaching practices, thus impacting student achievement. Qualitative research methods were used to identify and examine which PLC structure impacted teaching practices, student learning, and student achievement in high school classrooms. [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.]