The purpose of this study was to determine how the leadership practices and guiding values of a professional learning community affect the nature of the professional relationships among teachers. Three major findings are discussed related to the implementation of PLCs as a means to improve student achievement in low-performing schools. First, implementing PLCs in a low-performing, economically disadvantaged school requires non-traditional leadership. Second, PLCs in economically disadvantaged schools differ markedly from the textbook ideal. And finally, PLCs alone do not affect social mobility for students. Results from this study should prove useful to principals who wish to lead the development of professional learning communities in their districts.