The PISA survey shows that mathematics performance in Sweden has declined, raising questions about how critical thinking, a key component of PISA's mathematics tasks is addressed in teaching. The aim of this thesis is to explore how lower secondary mathematics teachers perceive critical thinking in the subject and how they work to promote it in their teaching. The study is based on a qualitative method, involving interviews with six lower secondary mathematics teachers and classroom observations of four of them.

The results show that teachers hold different views on what critical thinking in mathematics entails, which affects how they design their instruction. Despite differences in teaching methods, the teachers report similar challenges, such as large variations in students’ knowledge levels, limited understanding of concepts, and students’ reluctance to participate in discussions. The study highlights the need for clearer support structures and strategies to help develop students’ critical thinking skills in mathematics education.