The Experimental College Movement (also referred to as EXCO or EC) has taken several forms historically, but is generally a school within a school, based out of a college or university, that offers classes taught by not just traditional professors, but students and community members as well (often without grades and often free of charge or in some way associated with social or curricular change).
In the 1960s the idea took the form of a movement, with Experimental Colleges arising at San Francisco State College (later San Francisco State University) in 1964-65, at Tufts University and the University of California, Davis, in 1966, and the University of Washington and Oberlin College in 1968. In addition to these projects, which still exist today, some Experimental Colleges came in and out of existence, such as the Tussman Experimental College at the University of California, Berkeley, and at the University of Southern California. These projects reflect different approaches to the concept: some hold fast to the principle of cost-free courses, some offer courses for credit, some emphasize a community focus. More recently established Experimental Colleges exist at Haverford and in the Twin Cities.
And while EXCOs draw upon a long history of many radical community movements including Popular Education, Free Schools, Freedom Schools, Work Peoples' Colleges, etc., the original concept is often attributed to Alexander Meiklejohn, who spearheaded such a project at the University of Wisconsin, Madison and authored a book about the experience, The Experimental College, in 1932.