School leaders face potential conflicts between the demands of national and local education policy and the values and ethics that brought them into teaching and subsequently into school leadership. This article asks whether head teachers' values are changed by the policy context, and looks at incidents in head teachers' professional lives that have put their values to the test. It draws on case study work undertaken with one primary school and two secondary school head teachers in an English urban local authority. The article concludes that, for all the opportunities and limitations of educational policy, the greatest influence on the agency of school leaders is the personal history that has shaped their values and given direction to their moral compass.