CHICAGO (AP) — Mayor Rahm Emanuel asked a state court Monday to force Chicago school teachers back to work and end a weeklong strike he calls illegal.

Emanuel spokeswoman Sarah Hamilton said city attorneys asked the Cook County Circuit Court to force Chicago Teachers Union members off the picket line and back into classrooms.

The request, filed in Circuit Court of Cook County, argues the strike is illegal because state law bars the union from striking on anything but economic issues and that the work stoppage is focused instead on such issues as evaluations, layoffs and recall rights.

The filing also contends the strike presents a danger to public health and safety, partly because more than 80 percent of 350,000 public students rely on school meals for their basic nutrition; it says 50,000 others, including autistic students, depend on special instruction. And out of school, children more prone to fall victim to violence, it says.

“At a critical time in their lives, a vulnerable population has been cast adrift by the CTU’s decision to close down the schools, with consequent grave implications for the residents of the city of Chicago,” the court document says.

The union and school leaders seemed headed toward a resolution at the end of last week, saying they were optimistic students in the nation’s third-largest school district would be back in class by Monday. But teachers uncomfortable with a tentative contract offer decided Sunday to remain on strike, saying they needed more time to review a complicated proposal.

Emanuel fired back, saying he told city attorneys to seek a court order forcing Chicago Teachers Union members back into the classroom.

Teachers on the picket line at Mark T. Skinner West Elementary School on Chicago’s near West Side declined to comment before the lawsuit was filed Monday as the possibility of legal action loomed over them.

The strike is the first for the city’s teachers in 25 years and has kept students out of class, leaving parents to make other plans.

Working mom Dequita Wade said that when the strike started, she sent her son 15 miles away to a cousin’s house so he wouldn’t be left unsupervised in a neighborhood known for violent crime and gangs. She was hoping the union and district would work things out quickly.

“You had a whole week. This is beginning to be ridiculous,” Wade said. “Are they going to keep prolonging things?”

Months of contract negotiations have come down to two main issues central to the debate over the future of education across the United States: teacher evaluations and job security.

Union delegates said they felt uncomfortable approving the contract because they had seen it only in bits. The union will meet again Tuesday, after the end of Rosh Hashana, the Jewish new year.

“There’s no trust for our members of the board,” Chicago Teachers Union president Karen Lewis told reporters Sunday night. “They’re not happy with the agreement. They’d like it to actually be a lot better.”

Emanuel showed his frustration at the striking public school teachers in a written statement Sunday night.

“This was a strike of choice and is now a delay of choice that is wrong for our children,” Emanuel said.

The strike has shined a spotlight on Emanuel’s leadership more than ever, and some experts have suggested the new contract — which features annual pay raises and other benefits — is a win for union.

“I’m hard-pressed to imagine how they could have done much better,” said Robert Bruno, a professor of labor and employment relations at the University of Illinois at Chicago. “This is a very impressive outcome for the teachers.”

With an average salary of $76,000, Chicago teachers are among the highest-paid in the nation, and the contract outline calls for annual raises. But some teachers are upset it did not restore a 4 percent raise Emanuel rescinded last year.

Emanuel pushed for a contract that includes ratcheting up the percentage of evaluations based on student performance, to 35 percent within four years. The union contends that does not take into account outside factors that affect student performance such as poverty and violence.

The union pushed for a policy to give laid-off teachers first dibs on open jobs anywhere in the district, but the city said that would keep principals from hiring the teachers they think are most qualified.

The union has engaged in something of a publicity campaign, telling parents about problems that include a lack of important books and basic supplies.

Some parents said they remain sympathetic to teachers.

“I don’t think they’re wrong. The things they’re asking for are within reason,” said Pamela Edwards, who has sent her 16-year-old daughter to one of about 140 schools the district has kept open during the strike to provide meals and supervision.

Others said they understand why teachers are taking their time.

“As much as we want our kids back in school, teachers need to make sure they have dotted all their i’s and crossed their t’s,” said Becky Malone, mother of a second grader and fourth grader, who’ve been studying at home and going to museums over the last week. “What’s the point of going on strike if you don’t get everything you need out of it? For parents, it’ll be no more of a challenge than it’s been in the past week.”