In this thesis, critical thinking is presented as one of the key competencies of the modern education system. The thesis explores ways to integrate critical thinking into the educational process by examining various teaching methods and activities. The importance of critical thinking for the holistic development of students is highlighted, with an analysis of its theoretical foundations and potential applications in the school context. Emphasis is placed on adapting teaching content and methods to the individual needs of students and their developmental stages. The research findings suggest that active teaching methods involving collaboration and reflection can significantly influence the development of critical thinking in students. A distinctive feature of the thesis is the inclusion of methodological scenarios for upper primary school grades, which provide concrete examples of how this concept can be implemented in schools. The thesis explains the need for the continuous adaptation of teaching methods and the collaboration between teachers and students. It recognizes the importance of developing critical thinking as a trait of modern and active citizens, with particular attention given to the implementation of this concept within the Croatian educational system, along with the context and challenges it entails.