Union officials have said they are puzzled by the stance of Emanuel, the city's Democratic mayor, whom they accused of going back on promises to teachers, police officers and other civil servants, according to Rehak, the union board member.

"He has definitely been a huge disappointment," Rehak said. "He has disrespected virtually every middle-class person in this city."

Sen. Dick Durbin, D-Illinois, urged a quick resolution.

"Both sides need to get back to the table as quickly as possible and really stay in there, negotiate through the night if necessary," he said Monday. "Get it over with quickly so that we can get these kids back in school."

About 50,000 Chicago students who attend charter schools are unaffected by the strike and will remain in class. But that still leaves the vast majority of students, whose parents were encouraged by the school district to "explore other options for their children" as long as the strike continues.

"We know that a strike will put a strain on many families, and no one will be hurt more by a strike than our students," the district said on its website.

One of the organizations opening doors for students during the strike is Young Chicago Authors, which has a free program for part of the day for students in grades six through 12.

"In collaboration with core performance artists and special guests, young people will see the power of their voices in action through film, performance and discussion," the group said.

Still, some parents were concerned about what would happen to their children during the strike.

"If the kids are not in school, they're out getting into some kind of trouble ... when they should be in school, learning," said Shatara Scaggs, a mother of two children in kindergarten and first grade who opposes the teachers' decision to strike. "I think they should be in school getting an education."