This study explored a formal structure, the cohort model that a decentralized district put in place over a decade ago. Schools were clustered into cohorts to facilitate professional development for leadership teams for all 44 schools within the district. Drawing upon Senge's components of organizational learning, we used a single case study design with two embedded units to examine how a district created opportunities for organizational learning through the cohort model. Our findings revealed how this large district gave considerable autonomy to schools and at the same time created a coherent structure that facilitated both system-wide as well as within cohort professional development. The model also supported formal and informal relationships within cohorts and across the district. Our evidence showed how trusting relationships fostered strong collaboration amongst principals and led to higher levels of social capital and intellectual capital, which in turn enabled the schools and cohorts to practice the components of organizational learning. These schools and the district achieved sustained increases in student achievement.