While there has been considerable research activity in the area of middle management/middle leadership since the late 1990s, the concept remains under-theorised and ambiguities persist in relation to who middle managers or middle leaders are and what they do. The recent shift in terminology in the literature from 'middle management' to 'middle leadership' alludes to evolution in the roles these leaders play in schools. However, without a theoretical model to use as a point of reference it is difficult to describe the nature of such evolution and even more difficult to identify implications for teacher productivity, student outcomes and school effectiveness. This article proposes a model of middle leadership in schools based on an extensive review of the literature. The Middle Leadership in Schools (MLiS) model describes factors that influence middle leadership, possible influences of middle leadership on schools, a typology of roles middle leaders perform and how they might perform them. The article concludes with implications for research and theory building in a still-emergent area within the broader field of educational leadership.