The Chicago Teachers Union moved one step closer to a possible strike Wednesday.
The union's delegates unanimously approved a strike authorization vote, CTU said in a statement.
That will set up a vote on Sept. 26 in which all CTU members will decide if the union will go on strike. The earliest that teachers and union members could go on strike is Oct. 7, CTU said.
The latest development - moving the union one step closer to a potential strike - came just one day after students returned to class across the city.
The school year began in the midst of contract negotiations between CTU and the city, after the last Chicago teachers contract ended in June. CTU last went on strike in 2012.
Last week, the union rejected a contract offer from the city that was recommended by a third-party arbitrator and included a 16% pay increase over five years, equaling about $351 million.
But the teachers union said it was about more than just money, asking for smaller class sizes, as well as more special education teachers, social workers and librarians, among other requests.
Their rejection of that offer on Aug. 26 started the countdown clock to a possible strike, legally allowing the union to strike after 30 days.
The two sides were expected to return to the bargaining table Thursday, according to multiple reports.