A structured framework and attributes indicative for educators to work together collaboratively in learning communities are best practices in teaching. Principals in New Jersey face a state mandate to facilitate professional development using the school-based learning-communities process which is examined in this study. The focus of the research questions was to examine the principal's leadership role in facilitating the creation and use of best practices and a culture of adult learners. In this mixed-methods approach, qualitative data were collected through 8 semiformal interviews, 5 with elementary school principals and 3 with middle school principals, from the same suburban school district in New Jersey. NVivo software program was used to manage 4 emergent themes: (a) the role of the principal, (b) the characteristics, (c) hindrances, and (d) benefits and outcomes. Quantitative data were collected from 302 online teacher surveys. Results suggest that the school principal is the key change agent in the school, that leadership will produce long-term positive results, and that teachers work together to improve student achievement. The final project is a ready to use, "how to" guide designed to provide the building principal with a tool to facilitate the learning community process in their school. The implication for social change includes providing the building principal with a structured framework in which educators will work collaboratively in learning communities, as adult learners, to improve student achievement. [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.]