This report documents a study that examined what school leaders actually do to effectively lead schools. It then presents what this implies for policy and leadership development. Data for the study were collected from interviews with principals, vice principals, and teachers from 21 public, private, charter, contract, and magnet schools in 4 cities in 4 states. From the interviews came five major conclusions: (1) The core of the principal's job is diagnosing the school's particular needs and deciding how to meet them; (2) regardless of school type, leadership is needed in seven areas: instructional, cultural, managerial, human resources, strategic, external development, and micropolitical; (3) principals are responsible for ensuring that leadership happens, but they do not have to provide it; (4) a school's governance structure affects the ways key leadership functions are performed; and (5) principals learn by doing and acquire skills on the job. The results suggest that a variety of leaders and leadership models can work within schools. The report concludes with some suggestions about how district and state policymakers and colleges of education can change to better support the variety of leaders and leadership. (WFA)