This qualitative empirical study uses interview data from 16 secondary school students in Austria, who experienced lessons in Critical Mathematics Education (CME), to understand how students perceive a CME approach. Despite the long theoretical tradition and the existence of practical reports from the teacher perspectives, there is a lack of first-hand student data on the perception of CME lessons. In this study, students who had been introduced to CME lessons through at least one extensive CME problem participated in semi-structured interviews, which then were analyzed following a thematic analysis. The findings show that students find very different aspects of CME lessons to be noteworthy in a reflection, proposing that students are attracted to or challenged by different specificities of the CME classroom. Many students consider CME activities as non-mathematical as they go beyond mere calculations and easy applications. Often, students fail to identify mathematical learnings from CME lessons. However, the contexts of the CME tasks turned out to be meaningful and motivating for the students. The social organization of the CME classroom, which features discussions using mathematics to solve societal problems, was both new and attractive for the students. Our analysis offers more detailed insights into the perceptions of the students in the dimensions of the mathematics involved, the contexts of the CME problems, and the social organization of the lessons. We conclude that both more empirical research and more theory development are necessary to understand the perception of and introduction to CME in school.