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CHICAGO (AP/WGN) — Chicago students will head back to class Wednesday after leaders of the Chicago Teachers Union tentatively approved a plan with the district over COVID-19 safety protocols.

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

Neither side immediately disclosed details Monday evening.

“We know that this has been very difficult for students and families,” Lightfoot said. “Our goal throughout this entire process was to both get our students back to in-person learning as quickly as possible and prevent work disruptions for the rest of the school year.”

Issues on the table have been metrics to close schools amid outbreaks and expanded COVID-19 testing.

The Chicago Teachers Union voted last week to revert to online instruction and told teachers not to show up in person at schools as negotiations continued. District officials argued that schools are safe, a return to remote-only learning isn’t a good option, and blocked teachers from accessing online teaching systems. Meanwhile, families scrambled to adjust just two days after students returned to classrooms after winter break.

Lightfoot reiterated the danger of remote learning Monday night, saying the city’s previous stint of virtual instruction aided the loss of 100,000 CPS students, accounting for nearly a third of city schools’ population.

WATCH: Lightfoot speaks on CPS,CTU negotiations as final vote looms

Chicago Public Schools CEO Pedro Martinez says students may return to class tomorrow if desired. Addressing the media, Martinez noted 16% of CPS teachers showed up to work Monday, adding that three schools held in-person instruction.

Despite the back-and-forth with CTU, Martinez praised the tentative agreement reached.

“We are committed to the safety of our students. We are committed to the safety of our staff,” Martinez said. “We’re going to work together. There’s some really good things in this agreement..that build on procedures and safety protocols put in place. Expanded testing, having a stronger effort around supporting our school whether it’s contact tracing or initial investments of PPE.”

The district plans to distribute K-95 masks for students and staff, provide substitute teacher incentives, and the guarantee of receiving 350,000 antigen tests from the state. 

The teachers union asked the district to establish metrics to close schools in cases of COVID-19 outbreaks. CTU says those metrics were established as part of the tentative agreement. The union had hoped for a one week period of remote learning starting on Wednesday, Jan. 12, with a return to in-person instruction on Jan. 18, but agreed to the shortened timeline. 

CTU President Jesse Sharkey spoke via Zoom Monday night about the House of Delegates vote and bargaining with Lightfoot and CPS for students and teacher’s safe return to school buildings.

“We’re happy it’s over,” Sharkey said, “but we’re not happy we had to go through this in the first place.”