This article is inspired by conversations and correspondences with teachers relating to their real world experiences with CAS in the Danish upper secondary mathematics program. Our contribution is to view these experiences through a selection of mainstream mathematics education theoretical lenses. Using these lenses has led us to conclude that a strong reliance on CAS in upper secondary school provides new and efficient procedural solution strategies to classical problems (e.g., finding the monotony). On the other hand, these new strategies sometimes black-box central concepts that are the focus of the teaching (such as the derivative). This means that students who are trying to cope with mathematics might hang on to such procedural and pragmatic approaches, since they allow them to “deliver” and participate in class. On the down side, such students may never develop good perceptions of central concepts and topics, and are not even motivated to do so if they mainly meet tasks easily handled by CAS.