Some research suggests that development of professional learning communities might be the organizational strategy that could make school reform more successful. While most schools have not institutionalized the essential components of learning organizations, studies have demonstrated that these attributes must be developed if professional staffs are to realize the full benefit of organizational learning and in the process, create a context of improvement. The primary intent of this study was to learn and understand how principal behaviors influenced the development of shared leadership, shared vision, and supportive conditions; three essential dimensions of professional learning communities. Secondly, this study investigated how these conditions differed among schools which have and have not sustained high levels of student learning. Understanding the influence of principal leadership on conditions for organizational learning can be partially understood through either quantitative or qualitative methods. From this perspective, the mixed methods design utilized in this study allowed both qualitative and quantitative data to be analyzed and interpreted as evidence in understanding the study's problem. Principal and teacher focus-group interviews were used to create a deeper understanding of how principals worked to create conditions for organizational learning. Kouzes and Posner's (2002) Leadership Practices Inventory - Self and Observer Forms were utilized to identify, describe, and measure the perceived leadership practices of principals. The findings of this investigation suggest that principal leadership is a key factor in creating conditions for organizational learning and sustaining high levels of student achievement. Principals in this study who effectively identified and modeled espoused values were perceived to be highly visionary and appeared more effective at sharing leadership, inspiring vision, and creating supportive conditions. Principals who were able to develop a shared vision among staff created strong collaborative cultures characterized by an uncompromised focus on student learning. The findings of this study also indicated that principals who effectively Model the Way, Inspire a Shared Vision, and Enable Others to Act, distributed leadership among staff and demonstrated a systems orientation to leading.