This study aims to contribute to a better understanding of the antecedents and effects of educational leadership, and of the influence of the principal's leadership on intervening and outcome variables. A path analysis was conducted to test and validate a causal model. The results show no direct or indirect effects of educational leadership on student commitment; instead a reciprocal relationship was found between student commitment and strategic leadership. A range of antecedent variables appears to have more effects on the school culture than educational leadership has. Finally, the principal's vision has a substantial impact on his or her educational leadership behaviours. The findings suggest the importance of cognitive processes in order to understand the complex chain of variables through which principals have an impact on school effectiveness and school improvement. The results also underline the importance of conceptualizing leadership from a contingency approach. (Contains 4 figures and 2 tables.)