The appropriate choice of media is a key task in lesson planning. In the past years, there have been several studies which indicated potential in the use of digital media in the classroom. Nevertheless, these technologies are rarely used in everyday teaching. While one initially thought that this was due to the lack of infrastructure, it seems to be more due to a lack of skills. For this reason, the present study investigates what skills teachers need in order to teach functional relationships with dynamic worksheets, what skills pre-service teachers already possess and how these can be fostered.