The network Knowledge and Quality across School Subjects and Teacher Education (KOSS) brings together three cross-disciplinary educational research groups, rooted in several academic disciplines from Karlstad University, Sweden; University of Helsinki, Finland, and Univeristy College of London, Institute of Education, England. We seek to understand how educators and education systems can ensure that school-based knowledge building reaches its transformative potential. We draw upon the concepts ‘powerful knowledge’ and ‘epistemic quality’ to help us understand the qualities that knowledge building has when it is effective and empowering, and to help us understand how educational processes can build and develop these properties.