Updated 09/10/12 - 5:36 p.m.
CHICAGO (CBS) -- Thousands of public school teachers and their supporters have flooded downtown streets Monday afternoon, for a rally in front of Chicago Public Schools headquarters on the first day of the city's first teachers' strike in 25 years.
Crowds of teachers, parents, and other labor union members gathered at several spots downtown -- including Daley Plaza across the street from City Hall -- before making their way to CPS headquarters at 125 S. Clark St. for a 3:30 p.m. rally.
Virtually all of the protesters were dressed in red Chicago Teachers Union T-shirts, and many of them held picket signs with slogans like "Solidarity Forever," "On Strike For Better Schools," and "Fair Contract Now."
Teacher Sharon Scott said, "This is about veteran teachers, that have the right to a job, to have a job, instead of all the younger teachers that are being hired, and coming into CPS, and leaving us out, and basically making us destitute."
One teacher, who brought her granddaughter to the rally, said, "I see unity. I feel good about us buying in together as teachers."
Many drivers in downtown Chicago honked as they passed by crowds of protesters early Monday afternoon, while some passersby on foot cheered them on.
CTU officials estimated 5,000 protesters would take part in the rally.
By 5 p.m., many of those protesters had marched south from CPS headquarters to City Hall, and had surrounded the building in a ring of people donning red.
The protest march was creating havoc for drivers in the Loop, with several streets shut down to accommodate the protesters, leading to major traffic jams on other downtown streets.
The vast majority of protesters had dispersed by about 6:15 p.m.
Teachers and CPS administrators returned to the bargaining table at midday on Monday, but negotiations broke off for an overnight break. They resume Tuesday.
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