This paper addresses the role of the school principal in school improvement through secondary analysis of data collected from 98 elementary schools in Tennessee that participated in the School Improvement Incentives Project between 1983 and 1986. The paper explores an instructional leadership model as operationalized in measures of selected school context variables, principal gender, principal instructional leadership, school level instructional climate, school level instructional organization, and reading achievement. The paper examines the instructional leadership model developed by researchers at the Far West Laboratory (FWL) for Educational Research and Development with particular attention to the relationships among endogenous variables included in the conceptualization. The paper's analysis generally supports the FWL model. Results indicate that principals' instructional leadership appears to be exercised primarily through behaviors that shape school level instructional climate. The model suggests that principals can influence student learning by developing a clear mission that provides an instructional focus for teachers through the school. Appended are two instructional leadership models and estimated equations and matrixes. (SI)