The purpose of this mixed methods study was to explore the effects of professional learning communities on veteran teachers with three or more years of experience assigned to new grade levels or subject areas and the implications for school leaders. The specific research questions that framed the study were: (1) What do veteran teachers assigned to new grade levels or subject areas perceive to be the impact of professional learning communities on their change process? and (2) What role do school leaders play in supporting veteran teachers assigned to new grade levels or subject areas during the change process? During the first quantitative phase, the investigation analyzed veteran teacher perceptions of their schools using Southwest Educational Development Laboratory's "School Professional Staff as Learning Community Questionnaire" (SPSLCQ), developed by Dr. Shirley Hord. Veteran teachers, all members of PLCs, were surveyed from elementary, middle, and high school levels of a mid-sized Georgia school district, using descriptive statistical analysis. During the second qualitative phase, veteran teachers were interviewed to obtain more in-depth information regarding their professional learning and the role school leaders played in supporting their change process. Open coding revealed recurring themes and confirmed the quantitative results of the study. Veteran teachers perceived their professional learning communities to impact their change process by providing opportunities for collaboration, shared personal practice, and supportive conditions. Veteran teachers also perceived their school leaders to support their change process by encouraging open communication, creating a culture of learning, and empowering them to make decisions. [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.]