The slogan E pluribus unum sums up the strength that is the United States. It is this very strength that the socialist left seeks to undermine by turning our melting pot stew into a mixed salad.
One of the goals of the Communist Party, as stated in the Congressional record of 1963 was to downplay American history and the role of the founding fathers in the public schools, as well as dumbing down the curricula. The whole purpose is to surpress national pride, raise doubts about the moral quality of US gov't and create an unquestioning, malleable following for the leftist educators.
Don't get distracted, though. Dewey, the NEA, and a whole slew of others were funded by private corporate foundations, primarily Carnegie and Rockefeller.
Tax Exempt Foundations: Report of the Special Committee to Investigate Tax-Exempt Foundations and Comparable Organizations, House of Representatives, 83rd Congress, Second Session, on H. Res. 217 (House Report #2681). Pay particular attention to the section Foundations and Education, pp 134-168. Check it out.