This study builds on research which contends that just as effective principals must lead across a broad purview of responsibilities in order to build successful schools, so too must middle leaders. Decentralisation of school management has resulted in an expansion of school principals' responsibilities, contributing to a further distribution of leadership responsibility to middle leaders. This conception of middle leadership requires a shift in understanding of the nature of middle leaders' work. There is vast potential for middle leaders to contribute to their schools beyond subject administration, yet the research base yields limited insight on such work and on how middle leaders can be supported to accomplish it. This research finds that middle leaders who expand their leadership responsibilities do so in contexts that utilise school mission, policy enactment and organisational design as platforms for enhanced middle leadership. Copyright © 2018 Informa UK Limited, trading as Taylor & Francis Group.