Early childhood education teachers have been challenged with the demands for accountability in literacy and English language development, as well as kindergarten readiness skills of preschool children. Researchers have studied professional learning communities (PLCs) as a framework for professional development and student achievement. However, few have studied the effects of PLCs in preschool. The purpose of this qualitative case study was to explore how PLCs support preschool teachers in Head Start and other preschool programs. The research questions involved understanding teaching and learning opportunities for early childhood education (ECE) that can produce positive child outcomes. Using social constructivist assumptions, data collection began with interviews of the leadership team that oversees the ECE services within a suburban Southern California school district. Additional data was gathered from archival records, field observations, and interviews of 20 teachers clustered into 4 PLC groups. Observational data were coded from video recordings via checklists derived from the review of the literature. Interview data were coded for a priori themes based on the literature, were continually reviewed for additional emergent themes, and discordant data separated for later consideration. Coded data were analyzed thorough the sequential method outlined by Janesick, yielding 7 factors related to increasing teacher learning and 4 related to increasing student learning. These results were employed to create a district-wide PLC professional development plan for ECE teachers. The study has implications for social change by supporting collaborative cultures of teacher leadership that continually improve ECE instruction and student learning. [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.]