Based on Habermas' normative theory of religion in post-secular society, this paper elaborates on the organization of Islamic RE in public schools. Hereto, a brief sketch of the Habermasian concepts of reflexive religion and complementary learning processes will be given.Subsequently, the author addresses the role of RE in post-secular society and applies the aforementioned Habermasian concepts to confessional RE, with particular attention for Islamic RE in Belgium, where this subject is organized in state schools since 1975, but where it is also criticized today, in particular with regard to content, teacher-training, textbooks, and inspection. These deficiencies will lead us to one of the main problems of Islamic RE and of confessional RE in general: the absence of state control. Based on Habermas' ideas, the author concludes that it is up to the state to elucidate under which conditions confessional RE can be part of the regular curriculum, and to facilitate these conditions, e.g. by funding and co-organizing teacher training; by reviewing curricula and textbooks; by formulating a 'core curriculum', and by controlling teachers. If these conditions have not been met, confessional RE should not be a part of the regular curriculum in a liberal state.