Best instructional practice occurs when teachers work collaboratively. Many teachers in the target elementary school appeared to work in isolation, struggling to respond to the needs of low-performing students without the benefit of collaboration with colleagues. The purpose of this applied dissertation was to investigate the impact of a professional learning community (PLC) on teacher collaboration, teaching practice, and student achievement. Data were obtained from classroom observations, self-report surveys, student benchmark-test scores, focus-group interviews, content analysis of documents and artifacts produced in the PLC, and documents produced in the PLC book-study group. This inquiry was guided by the idea that a PLC would improve teacher collaboration and sharing of research-based teaching practice, which would have a positive impact on student achievement. In a PLC, educators meet regularly as a team to identify what students should learn and needed strategies and practices. The PLC in the target school was a regular, ongoing educational practice initiated by administrators and staff to increase collaboration and sharing of ideas, strategies, and practice. The results of this study indicated a PLC in the target school had a positive impact on teacher collaboration and teaching practice. However, results were inconsistent across grade levels for impact on student achievement based on benchmark test scores in reading and mathematics. Although benchmark test scores did not show an increase at most grade levels, data from focus-group interviews, reflective journals, and content analysis of documents provided evidence that teachers perceived teacher collaboration had an impact on student achievement. Based on study results, it is important for leaders in schools to continue to revisit and confirm the benefits of a PLC on teacher collaboration, teaching practice, and student achievement. [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.]