In this two-phased study, the researcher collected collective efficacy data from three Western New York schools where student achievement was improving and had been recognized as being in the top 35% of the region, where students living in poverty comprised more than 25% of the student body, and where the principal had been in place for at least three years. Survey data indicated that all three schools showed a stronger sense of collective efficacy for items that analyze teaching competency over teaching task. Following the survey analysis, semi-structured interviews took place in the school with the highest collective efficacy score. The findings indicate that collective efficacy in this one small school was more nurtured by the teachers than the principal and that district-level structures both positively and negatively influenced collective efficacy. Student diversity and pride among staff members emerged as positive influences on collective efficacy and the importance of relationships was underscored. The researcher proposes an updated model of collective efficacy where the four sources of efficacy are seen as separate entities and where analysis of the difficulty of the teaching task is reflected as more critical than analysis of teaching competence. [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.]