The aim of this study is to better understand the role of researchers and school leaders in supporting school improvement through data feedback in the context of more responsive forms of accountability in the Netherlands. A process evaluation was conducted concerning the first three years of a collaborative project of a multi-management group of 18 primary schools and a group of researchers. The results show that implementing a system of data feedback starting from a shared vision on the need to learn from data, fostered processes in the school of learning from data for school improvement. The results also show a growing inquiry habit of mind amongst school principals, whereas the researchers learned how to take their role in the collaboration by providing conditions that enhance school improvement from data feedback. The results indicate that the collaborative process can be characterised by several learning functions and thus contribute to a better understanding of how the conditions for data feedback and school improvement can be enhanced. (Contains 2 tables and 1 endnote.)