The results of effective principal leadership qualities on school improvement are often felt but very difficult to quantify. It is important to know which qualities are most important, which qualities result in the most effective leadership, which qualities are most valued by faculties, and which qualities have the greatest impact on school culture. The purpose of this study is not only to identify effective qualities, but to also understand how these qualities translate to determination and implementation of professional learning. The context of the inquiry includes the administrative staff in two middle schools within a large public school district in the United States. My study demonstrates the impact of principal effectiveness on the ability to evaluate instruction and relate such evaluation to student achievement data to determine and implement a professional learning plan for teachers