The purpose of this study is to examine the effectiveness of professional learning communities by comparing practices and strategies of content and grade level teams in middle schools. Utilizing data from student assessment, comparison of teams in this middle school was conducted to determine practices and conversations that have an impact on teachers' decisions about student learning. Understanding phenomenon that drives effective decision-making processes in teams of teachers creates an environment where shared leadership produces professional learning communities that are sustainable and systemic. A qualitative approach was conducted in the form of a case study to capture themes relevant to teachers' thoughts about effective and ineffective team experiences. Using interviews, focus groups, and observations, themes were compared through open-coding and gathering of team minutes/notes. Triangulation of these data revealed themes relevant to creating effective teams by focusing on; curriculum, team dynamics, leadership, professional development, and personal influences that effected teachers. These themes were found to be the most impactful elements when designing and sustaining professional learning communities in this middle school setting. [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.]