The purpose of this study is to assess to what extent public school principals experience role uncertainty and risk on the job and to examine the joint effect of school principals' leadership style and use of power bases on school outcomes, under perceived role uncertainty and role risk. Questionnaires were administrated to 191 school principals and to 954 teachers working in the Israeli elementary school system. Principals reported about their role uncertainty and risk. Teachers characterized their principal's leadership style and use of power bases. National test scores in math and students' average SES scores were used to indicate school effectiveness. Results show that uncertainty and risk are relevant and significant characteristics of public school environment. Moreover, these conditions have implications for the leadership style and use of power bases likely to promote school effectiveness. In short, employing harsh power bases by passive or transactional leaders is not likely to have a positive impact on school effectiveness compared to transformational leaders employing soft power bases such as charismatic and professional authority when encountering perceived uncertainty and risk. The study points at the dilemma created for professional behavior by turbulent circumstances and the need to choose between normative expectations encouraging preservation and conservativeness and unintuitive tendencies leading to proactivity and daring as means to promote school effectiveness. Recommendations for the training of school leaders and for educational policy setting are discussed. It is suggested that particular emphasis should be placed on the design of daily school routine to better enable school leaders to act proactively, without losing their institutional legitimacy.