Chicago’s standoff between its teachers union and the city has come to an end after a deal was secured that addressed enough of teachers’ concerns to reopen classes starting Wednesday.

On Monday evening, the Chicago Teachers Union (CTU) announced that it had struck a deal with the administration of Mayor Lori Lightfoot to enhance new COVID mitigation measures in schools.

The measure was approved by 73% of the union’s House of Delegates after details were shared about the negotiations with the mayor’s office. Lightfoot also announced that an agreement was struck on her Twitter account.

"Some will ask who won and who lost but no one wins when our students are out of the place where they can learn the best & where they’re safest," Lightfoot tweeted.

The deal includes expanded testing and contact tracing with more rapid testing kits being made available for schools. It also included criteria for when a school may close due to COVID-19 outbreaks.

If 40% of the student body is in isolation or quarantined, the school will move away from in-person to remote instruction. These rules are designed to be more flexible, so that if a higher period of community spread of COVID-19 is ongoing, the threshold for closing would lower.

Throughout negotiations, the CTU griped that current efforts at mitigating COVID-19 in schools were severely lacking. In its statement announcing the deal, the union claimed Chicago’s current contact tracing procedures have been riddled with problems, including delays of a week or more to notify educators and parents of positive cases.

It also criticized the refusal of the city to allow an opt-out option for testing. Lightfoot had previously referred to this idea as “morally repugnant,” a comment the CTU took issue with and rebuked by pointing to other jurisdictions that allowed it.

Last week, Chicago's public schools shut their doors after teachers and staff voted to start the new semester with remote learning courses, arguing that the current COVID-19 situation necessitated the move. Lightfoot and her administration were opposed to this decision, with the mayor criticizing the decision as an “illegal work stoppage” and disruptive to the lives of students and their families.

Chicago, which has over 345,000 students attending its public schools, has become the largest city to close its schools as a new semester resumes. Smaller cities, including Atlanta and Milwaukee, have shifted to a limited period of online learning as have a number of universities across the U.S. over COVID fears.

President Joe Biden weighed in by saying that the science shows it is safe for children to attend classrooms despite COVID-19.

New York City, which hosts the nation’s largest public school district, has chosen to remain open. Former Mayor Bill de Blasio and his successor Eric Adams have echoed Lightfoot by insisting that schools are safe for attendance and closing them was not an option. Adams has been insistent that school is the best place to be for children amid calls from city teachers to move to remote learning.