When new ideas or curriculum find their way into schools, it is the teachers’ job to transform them into teachable units. Transformations demand ongoing choices in dilemmas between structure and improvisation. This study examines one lower secondary school teacher’s planning and enactment of a unit in geography through participant observation and interview. It analyses tensions between structure and improvisation in his planning documents, enacted learning activities and retrospect explanations. Three main dilemmas are uncovered: The teacher has to balance between the school’s strict timeframes and his own aim of teaching for deep learning, between ambitious backward designed goals and the need to adjust in the enactment, and between giving his students scaffolds and opportunities to explore. He solves these dilemmas by cutting science content and integrating first language lessons into the unit, by creating a flexible progression plan structured by subgoals, and by scaffolding the students’ knowledge acquisition while letting them improvise in tasks. This article discusses what kind of literacy-practice these solutions create, and asks whether the following would help the students both see the core of social studies and navigate the subjects: explicitly discussing the division of labour between the subjects, framing the unit with a big idea, and refocus the scaffolds from knowledge acquisition to knowledge application.