Chicago teachers and City Hall reached a labor deal Thursday to end a bruising strike that kept kids out of school for 11 days, officials announced.

Teachers and students will be back in school on Friday. Both the Chicago Public Schools (CPS) and the Chicago Teachers Union (CTU) announced the deal.

"This has been a long journey," Mayor Lori Lightfoot tweeted Wednesday. "Unfortunately, I think there's a lot of harm that has been done to our young people."

Five of the missed 11 days will be made up, according to City Hall.

Class size was a sticking point in the prolonged labor talks, and the city has committed $35 million annually to reduce student-teacher ratio in K-12 classrooms, the union said.

Chicago's 360,000 public school students comprise the nation's third largest school system, trailing only New York and Los Angeles.

The teachers union represents more than 25,000 teachers and support staff. Separately, 7,500 members of the Service Employees International Union Local 73 were also out on strike, but had reached a deal on Wednesday.

"We feel like we achieved a lot of things," CTU President Jesse Sharkey told reporters. "There are some things we didn’t achieve, but it’s not a day for photo-ops and victory laps."

Lightfoot invited Sharkey to make a joint announcement, but the union president declined in a sign of the lingering bad blood.

"Frankly, our members are still out there on picket lines," Sharkey said.

"They don’t need to see me smiling with the mayor when in fact what they need to see is we have a tentative agreement, we have a return to work agreement."

CORRECTION (Oct. 31, 2019, 6:05 p.m. ET): A previous version of this article misspelled the first name of the president of the Chicago Teachers Union. He is Jesse Sharkey, not Jessee.