Although the importance of critical thinking skills for students when they enter university is widely endorsed, previous research has shown that incoming students show great variation in levels of critical thinking skills. The pre-university track of secondary education plays a major role in preparing students to think critically at university. The present study aims to investigate the way in which secondary education teachers think about and foster critical thinking skills to prepare their students for university. Semi-structured interviews with nine teachers showed that teachers do not have an unambiguous picture of critical thinking skills. Instead, teachers varied in their perceptions of the importance of critical thinking skills for university and in the practices they employ to foster these skills. It appears that teachers' perceptions and practices, firstly, depend on their images of university which are often based on their own study experiences, and secondly reflect the way they think about the cultivation of critical thinking skills and the transition to university. These results indicate that whether certain critical thinking skills are more or less encouraged in secondary education depends on the teacher.