Attending to the questions of how school leadership influences learning and achievement and what effective school leaders do, this document describes a measurement-based approach for studying and developing effective school leadership. The document details the conception, refinement, and psychometric properties of the Instructional Leadership Inventory (ILI), a self-report survey designed to assess the direct impact principals have on their schools. Responses regarding principals' efforts to define school mission, manage curriculum, supervise teaching, monitor student progress, and promote instructional climate and those responses regarding general characteristics of staff, school, and community are used in the ILI to uncover characteristics of effective leadership. Also described are the conception, development, reliability, and validity of the student version and teacher version of the Instructional Climate Inventory (ICI), a multiple-choice survey designed to flesh out and cross-check the information obtained via the ILI. Lastly, the document discusses the School Administrator Assessment Survey (SAAS), a modification of Maehr and Braskamp's SPECTRUM, which is designed to measure administrators' job satisfaction, commitment, self-concept, personal incentive, perception of job opportunities, and perception of instructional climate. Included are six tables and one figure. (46 references) (CLA)