This article is about enhancing critical thinking as a crucial aspect of the competence citizens need to participate in society. First empirical research into the question which instructional strategies are "effective" in enhancing critical thinking is reviewed. Characteristics of instruction that are assumed to enhance critical thinking are: paying attention to the development of the epistemological beliefs of students; promoting active learning; a problem-based curriculum; stimulating interaction between students; and learning on the basis of real-life situations. Research has failed to prove the effectiveness of programs especially devised to improve critical thinking (higher-order) skills. In the second part of this article, the various proposals for instructional formats for critical thinking are discussed from a social constructivist point of view. Learning to think critically is conceptualized as the acquisition of the competence to participate critically in the communities and social practices of which a person is a member. If education is to further the critical competence of students, it must provide them with the opportunity at the level of the classroom and the school to observe, imitate and practice critical agency and to reflect upon it. Learning contexts must be chosen which students can make sense of and in which they can develop a feeling of responsibility for the quality of the practice in question.