When Chicago teachers struck in '73

This from a yellowed copy of The Call I found, from back in March, 1973:

CHICAGO

For the third time in four years, Chicago teachers have shut down that city's school system -- the nation's third largest. About...25,000 teachers struck for decent wages and smaller classes as well as a shorter school year with no resulting pay cuts or lay-offs. The striking teachers also asked for more free preparation time for elementary school teachers, so that teachers would not have to act as hall and lunchroom monitors...

Unlike previous strikes in the Chicago school system, this one received massive support from the black and Latino communities. This year, the new union leadership [Pres. Robert Healey and V.P Jacqueline Vaughn, who would later become the union's first female black president--mk]  formed alliances with groups in the community like PUSH. 95% of the teachers supported the strike and the result was that nearly all of the demands were won.

In the Chicago strike, custodians (mostly black) refused to heat the school buildings, in support of the striking  teachers...