The purpose of this study was to describe teacher perceptions of the effects of Professional Learning Communities (PLCs), as designed by common planning of core subjects among high school teachers, on teacher efficacy in the public schools of North Georgia. The study sought to answer the following research questions: (1) Is there a difference in teacher selfefficacy as measured by the Teacher's Sense of Efficacy Scale (TSES) between high school teachers who participate in Professional Learning Communities linked with the organizational structure of common core planning and those who do not? and (2) What differences exist among teachers' description of the effects of common core planning on their teaching practices and on their self-efficacy? The first question was answered using the TSES. The second research question was answered through interviews with a purposefully selected sample of teachers. This research used mixed methods. Survey and interview data exploring teacher's educational experience in Professional Learning Communities designed with and without common core planning were collected. Survey results provide evidence of a positive relationship between classroom related components of teacher efficacy and Professional Learning Communities linked with the organizational strategy of common core planning among the unit of analysis--the teachers. This study added to the existing body of knowledge about the use of Professional Learning Communities in high schools. Implications for researchers, policy analysis, and practitioners were identified.