A teacher's practical knowledge contains the teacher's beliefs about the goals, values and principles of education that guide his or her actions in the classroom. There is still a lack of knowledge about how teachers' practical knowledge influences their teaching. The present study examines student teachers' practical knowledge in the context of teaching climate change in elementary schools. Participating student-teachers planned their lessons using the principles and ideas of inquiry-based science teaching and the communicative approach. The same two approaches were applied in analysing the lessons, providing a broader basis on which to study student-teachers' beliefs about teaching science. The analysis revealed different levels of success in terms of implementation of inquiry-based learning; the communicative approach was not comprehensively realised in any class. Stimulated recall interviews highlighted that most student-teachers possessed sufficient knowledge to reflect on their lessons and the necessary awareness to use the communicative approach. By comparing the results of lesson plan analysis, communication analysis and stimulated recall interviews, we can better understand student-teachers' practical knowledge in the classroom.