A recurrent discussion in the field of education is how to build linkages between educational research and school practice. Cross-professional collaboration between researchers and school practitioners can contribute to the interplay between practice-based research and school development. The aim of our study is to obtain a better understanding of how a productive interplay between practice-based research and school development is established in the context of 19 research and development (R&D) projects in secondary education. Data from semi-structured interviews with school practitioners and researchers involved in the projects, observations of project meetings and document analysis were used. A productive interplay, in which practice-based research informed school development, was found in two-thirds of the R&D projects. Important conditions in these projects include closing the feedback loop from research to school practice, and making clear agreements on communication and on division of roles and tasks.