This paper explores how the culture within a Danish university study programme affects students' aspirations of becoming a high school chemistry teacher. We draw on ethnographic fieldwork and qualitative interviews to describe and analyse the culture of the programme. In the analysis we foreground the case of two students to understand their identity negotiations and changes in their teacher aspirations over time. By combining a 'domains-of-power framework' with the concept of 'science identity', we show how everyday practices formed a culture of power that positioned research in the centre and teaching as a less attractive career path. By unfolding the subtle mechanisms that together form a culture of power, which works both to include and exclude, we show the ways in which the two student's aspirations for becoming high school chemistry teachers somewhat diminished over time. The study concludes that negotiating a science identity at a research-intensive university programme, makes it almost impossible to develop and keep an aspiration for becoming a high school teacher. To address the current and future shortage of science teachers across Europe, our findings underline the need for a more inclusive culture at the university to support science students' diverse aspirations.