Teacher collaboration is essential for the improvement of student achievement and teacher performance. Classrooms comprise a variety of learners with individual learning needs that must be met for effective learning to take place. In the past, teachers have taught in isolation without the assistance of collaboration. A professional learning community (PLC) is a model that promotes staff professional development as a critical improvement to student learning. This type of professional development is most effective when it is collaborative, collegial, and involves inquiry and problem solving. The theoretical framework that guided this study was collective inquiry, which postulates that when educators work collaboratively in recurring cycles of collective inquiry and action research, they achieve better results for the students they serve. An explanatory case study design was used to investigate how teachers use collaboration in PLCs to enhance instruction and student achievement. Three teams of teachers from 4 academic disciplines were interviewed and observed. Interviews were transcribed verbatim, and data were analyzed using an inductive process to identify themes. Findings indicated that teacher performance and student achievement are positively affected by the opportunities of collaboration. One recommendation would be for school personnel to conduct a book study about professional learning communities such as texts that describe how PLCs changed schools from low performance to high performance schools. The resulting project and recommendations may promote a deeper understanding about how structured PLCs promote teacher discussion and reflection that may lead to improved future instructional strategies, teaching methods, and planning of authentic assessments. [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/en-US/products/dissertations/individuals.shtml.]