Most of the historiography of open-air-schools - and this is an understudied topic - is strongly influenced by the self discourse of the "believers" of the open-air-movement. E.g., one can easily recognize the assumptions that open-air-schools were laboratories of educational experiments or that their teaching methods fit in progressive education. The proposition we advance is that of a more complex relationship between the educational space and the educational act, between "traditional" and "progressive education": On the basis of the Belgian example (first half of the 20th century) we will challenge the historiography and problematize the idea that open-air-schools unconditionally contributed to a progressive education. In our view, and according to the German literature on "Reformpadagogik" we demonstrate that open-air-schools were as "schoolish" as "ordinary" schools and were no real alternative for traditional education. They were rooted in the same modernization, i.e. "educationalization" processes as the traditional schools.