The contribution is divided into three parts; first, [it tries] ... to uncover the Decrolyians'discourse concerning school architecture. On the basis of original sources, [the authors] ... look at the manner in which Decroly's and his disciples' thoughts on school buildings expressed themselves in the material heritage. Subsequently, Decroly's own school location is described and the question is raised as to how the developed environment was integrated into the pedagogical practice. In the final section, we study the utopian blue-print by the architects Renaat Braem (who nowadays is still considered one of the most important representatives of modern architecture and modern urban development in Belgium) and Jack Sokol, dating back to 1946. This had been a megalomaniacal project which was described both by the archtitects mentioned above and by the Decrolyians as a break with the existing school buildings, the ancient temples of pedagogy, in which one professed one's faith in the old didactics. It links up with the body of thought of an international plea which had been discussed during the first half of the 20th century, mainly in reform-pedagogical circles. The fact that the Decrolyians did, in the end, not realize their project of a renewable architecture was not so much the result of their persistent skepticism regarding one or the other school-architectonic determinism, which would transport the school building beyond the pre-eminence of its flexible use within the framework of the active method, it was simply due to limited financial resources.