The purpose of this study was to determine variance in mean levels of teacher self-efficacy (TSE) and its three factors--efficacy in student engagement (EIS), efficacy in instructional strategies (EIS), and efficacy in classroom management (ECM)--based on participation and time spent in professional learning communities (PLCs). In this cross-sectional study, 123 teachers from two similarly profiled high schools in one, New Jersey urban public school district were surveyed using the Teacher Sense of Efficacy Scale (Tschannen-Moran and Hoy, 2001). An independent sample t test was used to measure variance in mean levels of TSE, ESE, EIS, and ECM between two independent groups, those teachers who did participate in PLCs and those teachers that did not participate. Results revealed no statistically significantly different mean composite and factor efficacy levels based on participation in PLCs. An analysis of variance was used to measure variance in mean levels of TSE, ESE, EIS, and ECM among four independent groups, (a) those that did not participate in PLCs, (b) those that participated in PLCs one day a week, (c) those that participated in PLCs two days a week, and (d) those that participated three or more days a week. Results revealed statistically significantly different mean levels of TSE and ESE between those that did not participate in PLCs and those that did participate in PLCs three or more days a week. In other words, those teachers that participated in PLCs three days or more a week had significantly higher TSE and ESE beliefs than those that did not participate in PLCs. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]