This paper shares findings from a recent study that engaged a group of Kenyan teachers in a review and development of interpretive materials through a participatory action research framework. It focuses on critical contextual reviews of interpretive materials in non-formal organisations and development of similar materials in schools with teachers. Social interactions between teachers and non-formal educators enabled the sharing of ideas, skills and techniques on materials development processes. This provided a basis for developing interpretive materials to support environmental learning within school grounds. A teacher-centred approach to materials development as argued in this paper seeks to respect the needs of schools within their social and historical contexts. It further challenges the conventional top-down approaches in which non-formal educators are creators of materials and teachers are viewed as "technicians" who implement the materials in schools. The paper offers some tentative guidelines on the development of interpretive materials in schools. (Contains 1 table.)