The New York City Teachers Union shares a deep history with the American left, having participated in some of its most explosive battles. Established in 1916, the union maintained an early, unofficial partnership with the American Communist Party, winning key union positions and advocating a number of Party goals. Clarence Taylor recounts this pivotal relationship and the backlash it created, as the union threw its support behind controversial policies and rights movements. Taylor's research reaffirms the party's close ties with the union—yet it also makes clear that the organization was anything but a puppet of Communist power.

Reds at the Blackboard showcases the rise of a unique type of unionism that would later dominate the organizational efforts behind civil rights, academic freedom, and the empowerment of blacks and Latinos. Through its affiliation with the Communist Party, the union pioneered what would later become social movement unionism, solidifying ties with labor groups, black and Latino parents, and civil rights organizations to acquire greater school and community resources. It also militantly fought to improve working conditions for teachers while championing broader social concerns. For the first time, Taylor reveals the union's early growth and the somewhat illegal attempts by the Board of Education to eradicate the group. He describes how the infamous Red Squad and other undercover agents worked with the board to bring down the union and how the union and its opponents wrestled with charges of anti-Semitism.