Previous subject-specific education research has shown that education in social studies subjects is dominated by strong subject traditions, while current social issues are seldom addressed and the connection to academic disciplines is weak. Putting this result into context, we discuss how the debate initiated by Michael Young about 'powerful knowledge' as a curriculum principle for the selection of school knowledge gives important theoretical insights. However, we argue that these insights can be developed further by linking them to continental "Didaktik" theory, in particular to Wolfgang Klafki's models of 'categorical Bildung' and 'critical-constructive didactics' and Ingrid Carlgren's perspective on teaching as different knowledge practices. These ideas make clear the link between the selection of knowledge at curriculum level and the selection and transformation of knowledge at classroom level. Based on this theoretical argument, we discuss how researchers and teachers can collaborate around the selection and transformation of knowledge in a school setting, thereby contributing to a knowledge reservoir for the teaching profession. We conclude with a discussion of an ongoing case study taking place in an upper primary school in Sweden, which exemplifies our theoretical argumentation, showing how a 'time-geographical' perspective can inform teaching about migration as a phenomenon and current social issue.