I _+suspect+_ but no proof, that the GI Bill introducing millions of regular folks to university that normally wouldn’t have been able to afford it, exposed them to the more surprising ideas found inside… The dates match anyway. 1944 American Legion introduces GI Bill. 1947 Congress passes it. 1951 “Do colleges *have* to hire red professors”? cover I showed above. https://en.wikipedia.org/wiki/G.I._Bill

Emphasis on learning by doing – hands-on projects, expeditionary learning, experiential learning
Integrated curriculum focused on thematic units
Strong emphasis on problem solving and critical thinking
Group work and development of social skills
Understanding and action as the goals of learning as opposed to rote knowledge
Collaborative and cooperative learning projects
Education for social responsibility and democracy
Integration of community service and service learning projects into the daily curriculum[2]
Selection of subject content by looking forward to ask what skills will be needed in future society[3]
De-emphasis on textbooks in favor of varied learning resources
Emphasis on lifelong learning and social skills
Assessment by evaluation of child’s projects and productions

https://en.wikipedia.org/wiki/Progressive_education