Democratic Chicago Mayor Rahm Emanuel turned to the courts today to try to force the city's 29,000 striking teachers to return to work.
The Chicago teachers union decided on Sunday to continue its week-long strike, extending a stand-off with the mayor over teacher evaluations and job security.
Mayor Emanuel said he would seek a court order to end the strike, which he claimed was illegal under state law.
Union delegates had declined to vote on a settlement worked out with officials over the weekend.
Union president Karen Lewis said that teachers want the opportunity to discuss the offer on the table.
"Our members aren't happy," Ms Lewis said. "They want to know if there is anything more they can get. They feel rushed."
She said the soonest classes could resume is Wednesday.
The walkout, the first in Chicago in 25 years, had stopped classes for 350,000 students.
It poses a high-profile test for teachers unions which have seen their jobs threatened.
Unions have pushed back against efforts to expand part-private charter schools, bring in private companies to run schools branded failures and link teacher evaluations to student marks.
The mayor and union agreed in July to implement a longer school day by rehiring 477 teachers who had been laid off rather than force teachers to work longer hours. But talks stalled on other issues.
Chicago's long history as a union stronghold has worked to the teachers' advantage. As they walked the picket lines, they were joined in solidarity by many of the very people who were most inconvenienced by the work stoppage - the parents.
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