In an effort to increase collaboration and support teachers in a formalized way, schools and districts have put structures in place for teachers and afforded them the time to participate in professional learning communities. This opportunity for teacher collaboration can impact the professional growth that is essential in moving a teacher's practice forward. By working together, teachers can improve their instructional practice, identify instructional strategies that are most effective, and impact student achievement and learning. Despite having multiple resources and training related to PLCs, there remains the need to better understand and identify what effective PLC groups use and do to make them successful. Even when some of these attributes can be articulated, there still remains a need to better understand the protocols and support that directly influence success. This qualitative study was designed to determine the attributes of successful PLCs at the secondary level. The researcher explored the views and experiences of junior high and senior high PLC members, the protocols, and the training and supports that assist teachers. The participants in this study were twelve teachers from two schools, a junior high and senior high school, in a large suburban school district. The participants were chosen from these two schools where principals have self-identified their campuses as ready to refine their professional learning practice through participation in a cohort. All of the teachers were engaged in campus wide PLC professional development related to data teams. The teachers voluntarily participated in focus groups to express views and share their own personal PLC experiences. The focus groups were audio-recorded and transcribed before being analyzed. The findings of the study identified the attributes, protocols and supports that the teachers perceive as necessary to implement successful professional learning communities, such as collaboration, data- and student-focused mindset and practices, assessments, tools, administrator support, protected time and communication. The teachers shared stories to describe their experiences, as well as the perceived successes of engaging in professional learning communities. The findings could be used to help other educators prepare for or refine the implementation of PLCs at their schools. [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.]