In this paper we explore the concept of the middle tier in education systems, outlining how it is a crucial element that links high-level education policy to the practices that are carried out in schools. Reflecting on the similarities and differences in the profiles of the middle tiers of the four nations of the United Kingdom (UK), we observe how they are part of a complex educational ecosystem. While noting that there are variations in the profiles of the middle tiers we also highlight how they share some common functions that are key to mediating the way that policy links with schools. Using a four nations comparative approach to analyse the middle tier allows us a more nuanced understanding of how education policy works in general, but also how policy works in each particular national context.