This paper traces the development of Inclusive Inquiry, a new approach to the promotion of inclusion in schools. It explains how this builds on a programme of research carried out by the authors over a period of 20 years. Central to the approach is dialogue amongst teachers and their students about how to make lessons more inclusive. This involves children becoming researchers who learn how to use research techniques to gather the views of their classmates, as well as observing lessons. The approach was refined as a result of a three-year action research study carried out with a network of eight secondary schools, in three European countries. It was then trialed in 30 primary schools, in five European countries. In each country a team of university researchers supported, recorded and analysed the action research as it occurred, using observations, interviews and surveys. The paper provides an analysis of the impact on the thinking and practices of teachers, and on the attitudes and engagement of students in learning. It is argued that Inclusive Inquiry is an approach that facilitates dialogues that can lead to transformations of practices and thinking, and the development of inclusive schools. Some of the challenges involved in using the approach in schools are identified.