This study investigated how core content high school teachers perceive the collective efficacy of faculties of their schools and whether those teachers who were involved in high school collaborative teams which met daily within the school day for instructional purposes had a greater perception of collective efficacy than those who were not. This study considered how teachers within these teams perceive the collective ability of the faculty as a whole. "Collective efficacy is the judgment of teachers in a school that the faculty as a whole can organize and execute the courses of action required to have a positive effect on students" (Goddard, Hoy, & Woolfolk Hoy, 2004, p. 4). Four hundred thirty-four high school teachers in core content areas were surveyed on their perceptions of their school's collective efficacy using the Collective Efficacy Scale-Form L developed by Goddard, Hoy, and Woolfolk Hoy (2000). This study was designed to: verify if teachers who were provided with daily time to collaborate on instructional issues had a greater perception of collective efficacy than those who were not provided daily collaboration time, determine the frequency of collaboration time that was needed to impact significantly teachers perceptions of collective efficacy, and examine whether the teachers' content or subject matter impacted perceptions of collective efficacy. Responses from the participants were analyzed using parametric and non-parametric t-tests, tests for equality of variances, parametric and non-parametric Analysis of Variance, and pairwise comparisons. Findings suggest that the perception of collective efficacy is significantly affected when teachers collaborate compared to those who do not. Further, it was found that when teachers collaborated three or more times per week, collective efficacy perceptions were significantly and positively affected. These findings add to the growing body of research on collective efficacy as it relates to professional learning communities and may inform principals and school system leaders that collaborative time is a vehicle to increase collective efficacy. The provision of collaborative time will require principals to create flexible schedules that allow for teacher collaboration on instructional issues at least three times per week. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]