Leadership has long been acknowledged as a significant dimension in effective school functioning and, indeed, school leaders can play a substantial role in professional development of staff. Here we have centred on the practices of leading as opposed to the qualities or characteristics of leaders, and this is emphasised by our use the term 'leading' rather than 'leadership'. In this article we explicitly focus on the leading practices of practitioners we describe as middle leaders. Middle leaders are those with an acknowledged position of leadership but also a significant teaching role. Here we present data from a cross national study of middle leaders in Australian primary schools and Swedish preschools which investigates the leading practices of middle leaders in educational contexts. The article draws on interviews with 22 teachers who have been given the responsibility for leading the practice development of their colleagues; these interviews give voice to this distinctive group of schools leaders. In particular, the article draws on the theory of practice architectures to examine the social nature of the language, activities and relationships of leading 'in the middle', and the particular conditions or practice architectures which enable or constrain the development of middle leading practices in education. From this analysis we conclude with a definition of middle leading that includes positional, philosophical and practice dimensions. This could then be used to inform the domains of higher education, policy development and school education globally where middle leading practices are well established.