This article deepens the knowledge of middle leaders' impact on school improvement and organisation development. More precisely, it focuses on how middle leaders from comprehensive schools and preschools translated improvement strategies and tools from a municipal course on leading school improvement into their own organisations. It is based on interviews with middle leaders, teachers, and principals at two schools and two preschools. Translation theory is used as a theoretical frame. The findings show that the middle leaders translated improvement strategies based on local needs, and for several reasons: for clarification and reduction of roles and improvement areas; structuring improvement work; engaging and involving colleagues in school improvement; and developing a professional culture. When taking the role of translators, the middle leaders became central to progressing the developmental elements of local school organisations. The study recommends investing to provide middle leaders with improvement strategies and an understanding of translation theory to enable translations that aid the development of school organisations.