CHICAGO (AP) — Chicago schools are poised to resume classes this week after leaders of the Chicago Teachers Union approved a plan with the district late Monday over remote learning and other COVID-19 safety protocols.

Both sides had been locked in an increasingly nasty standoff that canceled classes for four days in the nation’s third-largest school district. The deal, which would have students in class Wednesday and teachers a day earlier, still requires approval by the union’s full 25,000 members, according to the union.

Neither side immediately disclosed further details Monday evening. Issues on the table have been metrics to close schools amid outbreaks and expanded COVID-19 testing.

“We know this has been very difficult for students and families,” Mayor Lori Lightfoot said at an evening news conference. “No one wins when students are out.”

The Chicago Teachers Union voted Monday evening to suspend their work action from last week calling for online learning until a safety plan had been negotiated or the latest COVID-19 surge subsided. The district, which has rejected districtwide remote learning, responded by locking teachers out of remote teaching systems and docked pay.

Negotiations over the weekend failed to produce a deal and rhetoric about negotiations became increasingly sharp. Some principals canceled class Tuesday preemptively and warned of further closures.

Earlier Monday, Union President Jesse Sharkey said the union and district remained “apart on a number of key features” that teachers want before returning to classrooms. He also accused Lightfoot of refusing to compromise on teachers’ main priorities.

“The mayor is being relentless, but she’s being relentlessly stupid, she’s being relentlessly stubborn,” Sharkey said, playing on a reference the former prosecutor mayor made about refusing to “relent” in negotiations. “She’s relentlessly refusing to seek accommodation and we’re trying to find a way to get people back in school.”

Lightfoot accused teachers of “abandoning” students by refusing to teach in-person. She also shot back at the union president.

“If I had a dollar for every time some privileged, clouted white guy called me stupid, I’d be a bazillionaire,” Lightfoot, who is Black, told WLS-TV.

By evening she had said she was optimistic with the latest proposal, which went to union leaders for a vote.

Chicago shares pandemic concerns with other districts nationwide, with more reverting to remote learning as infections soar and staff members are sidelined. But the situation in union-friendly Chicago has been amplified in a labor dispute that’s familiar to families in the mostly low-income Black and Latino district who saw disruptions during a similar safety protocol fight last year, a 2019 strike and a one-day work stoppage in 2016.

The union wanted the option to revert to remote instruction across the roughly 350,000-student district, and most members had refused to teach in-person until an agreement, or the latest COVID-19 spike subsides. But Chicago leaders reject districtwide remote learning, saying it’s detrimental to students and that schools are safe. Instead, Chicago opted to cancel classes just two days after students returned from winter break.

Parents and advocacy groups stepped up calls Monday for quicker action in the dispute where both sides have already submitted complaints to a state labor board.

A group of parents on the city’s West Side — near the intersection of largely Black and Latino neighborhoods — demanded students get back to class immediately.

Cheri Warner, the mother of 15-year-old twins, said the sudden loss of in-person learning has taken a toll on her family.

One of her daughters has depression and anxiety, and winter is always difficult. Losing touch with her friends and teachers adds to that burden, Warner said.

The girls “missed their whole eighth grade year and it felt like they weren’t really prepared for high school,” Warner said. “They’re all trying to figure out how to catch up and it’s a really stressful situation.”

Other parents said the district needs to do more

Angela Spencer, an organizer with the Kenwood Oakland Community Organization and a nurse, said she’s concerned about her two kids’ safety in schools. Spencer, who said she works as a nurse, said her kids’ schools weren’t adequately cleaned before the pandemic and she has “no confidence” in the district’s protocols now.

At the same time, seven families, represented by the conservative Liberty Justice Center in Chicago, filed a lawsuit in Cook County over the closures, while more than 5,000 others have signed a petition urging a return to in-person instruction.

District officials, who call the union action “an illegal stoppage” have kept buildings open for student meal pickup and said that schools with enough staff can open their doors to students. Some teachers have shown up; district officials estimated about 15% of teachers did so Friday.

By Monday, three schools, including Mount Greenwood Elementary, were able to open, according to district officials. Parents at the largely white school on the city’s southwest side expressed relief.

City officials argued that schools are safe with protocols in place. School leaders have touted a $100 million safety plan, including air purifiers in each classroom. Roughly 91% of staff are vaccinated and masks are required indoors.

Union officials have argued the safety measures fall short amid record-breaking COVID-19 cases and the district has botched testing and a database tracking infections.