During the 1940s and 1950s the U.S. Communist Party upgraded and broadened its adult education schools, abandoning or ideologically modifying the militant pedagogical centres that had sprung up during the 1920s and 1930s in many American cities. In New York the transformation was complicated as two Party schools (the Workers School and the School for Democracy) merged with each other to create in 1943 the Thomas Jefferson School of Social Science. The California Labor School in San Francisco was the West Coast counterpart of the Jefferson School. The extent of this Communist pedagogical empire may be news to people, since no adequate scholarly investigation has been made of what, between 1923 and 1957, was possibly the largest system of adult education in America--until non-Communist colleges discovered the cash cow of continuing education. Having written general descriptions of both the Jefferson and California Labor School elsewhere, the author shall explore in this paper some of the political and pedagogical battles that "ended" the Communist educational system during the period called (using inaccurate but irreplaceable vocabulary) McCarthyism. (Contains 53 notes.)