Both sides were careful not to describe the deal as a final agreement. They expected to spend the weekend working out details before union delegates are asked to vote on the package, probably sometime Sunday.
Chicago School Board David Vitale said the "heavy lifting" was over after long hours of talks placed "frameworks around all the major issues."
The school district and union negotiators "put things on the table over the last few days to help each other" and put schools on track to reopen next week, Vitale said.
"Our kids are going to get the time they need in this school year, and they're going to get the time they need in the school day. And our teachers are going to get the respect they deserve for their hard work with our kids," he added.
Robert Bloch, an attorney for the Chicago Teachers Union, said union leaders updated delegates on the progress at a meeting Friday afternoon.
"It's been a very difficult agreement," Bloch said. "This has been one of the most difficult labor contracts negotiated in decades. Many of the core issues of the contract have been worked out, but not all of them."
About 15 minutes after union President Karen Lewis entered the delegate meeting, delegates could be seen through the windows cheering and applauding, some of them on their feet and pumping their fists in the air.
Journalists were not allowed inside, and there was no way to know what they were applauding.
When it's complete, the union's bargaining committee expected to recommend the contract proposal to the membership, Bloch said.
"And if we have been listening to the membership well and have heard their concerns, then that agreement will be accepted by our membership overall," he said.
The walkout, the first by Chicago teachers in 25 years, canceled five days of school for more than 350,000 public school students who had just returned from summer vacation.
The union's demands included a plan for laid-off instructors to get first dibs on job openings and for a teacher-evaluation system that does not rely heavily on student test scores.
The strike by more than 25,000 teachers in the nation's third-largest school district idled many children and teenagers, leaving some unsupervised in gang-dominated neighborhoods. It also has been a potent display of union power at a time when organized labor has lost ground around the nation.
The union has been trying to win assurances that laid-off but qualified teachers get dibs on jobs anywhere in the district. But Illinois law gives individual principals in Chicago the right to hire the teachers they want, and Mayor Rahm Emanuel argues it's unfair to hold principals accountable for their schools' performance if they can't pick their own teams.
The district offered a compromise. If schools close, teachers would have the first right to jobs matching their qualifications at schools that absorb the children from the closed school. The proposal also includes provisions for teachers who aren't hired, including severance.
It wasn't immediately clear if the union had accepted the proposal.
Readers of the Sun-Times opened the paper Friday to a full-page letter to Emanuel written by the Boston Teachers Union.
In the letter, the union reminded readers that some of the things Chicago teachers are fighting have long been available to Boston teachers, including the right to let teachers with seniority move into jobs in other schools if their schools close down.
Perhaps more significantly, the union took Emanuel to task for the contentiousness of the negotiations, putting the blame on the mayor's shoulders.
"Perhaps you can learn from us – and begin to treat your own teaching force with the same respect," the union wrote.
Meanwhile, Chicago teachers said they were planning a "Wisconsin-style" rally for Saturday, regardless of whether there is a deal on the contract.
The union has won widespread support from other teachers unions around the country, and a couple of hundred Wisconsin teachers planned to come to Chicago to join the event.
"It's really sort of a spontaneous kind of organizing," said Bob Peterson, president of the Milwaukee Teachers' Education Association, which unsuccessfully sought the recall of Gov. Scott Walker.
Until this week, Chicago teachers had not walked out since 1987, when they were on strike for 19 days.