Examines the characteristics (essential skills and knowledge) of middle-level leadership from the perspectives of the principals themselves based on data collected from middle-school principals in Pennsylvania and New Jersey, using surveys and semistructured interviews. Discusses seven themes that emerge from an analysis of the data, for example, viewing parents as partners. Presents a three-part model of principal leadership grounded in the concept of "developmental responsiveness." (Contains 62 references.) (Authors/PKP)