CHICAGO — Mayor Rahm Emanuel asked a state court today 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.

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.