This article explores a reciprocal relationship between leadership capacity and collective efficacy in a pre-K-8 school in the Southern United States that continually advances as a professional learning community. Survey data from this mixed methodology study showed significant positive correlations among subgroup scales measuring leadership capacity, collective efficacy, and professional learning community dimensions. Additionally, school performance, as measured by accountability systems, resulted in growth and sustainability of student achievement. The interviews made these findings come alive through four emergent themes: high leadership capacity; a strong sense of collective efficacy; continual and undeviating focus on learning for students and teachers; and a strong sense of collective responsibility, collaboration, and teamwork. This study provides clear evidence that capacity building and collective efficacy can be enhanced through success as a professional learning community. (Contains 1 table.)