• The Chicago public school system is the first of the largest districts in the nation to shut its doors amid a surge of Covid infections.
• The teachers' union voted to switch back to remote learning until infections subside or the mayor implements more safety measures.
• Chicago Mayor Lori Lightfoot called the union's decision an illegal work stoppage.

Chicago school leaders canceled classes Thursday for a second consecutive day after failing to reach an agreement with the teachers union over Covid safety protocols in the nation's third-largest school district.

The Chicago Teachers Union sought to revert to remote instruction during the latest surge of infections and while both sides hammer out a deal. But Chicago Public Schools leaders have said remote learning didn't work and schools can safely remain open with protocols in place.

The move to cancel classes and activities Thursday affects roughly 350,000 students and came after closed-door negotiations Wednesday failed to produce a deal. The issues include metrics for closing schools.

"We have no choice but to cancel classes tomorrow," Schools CEO Pedro Martinez said at a Wednesday evening news conference.

The Chicago public school system is the first of the largest districts in the nation to shut its doors amid the new Covid surge. New York City Mayor Eric Adams stressed earlier this week that schools would remain open. Los Angeles county schools have not returned to online learning, but ordered students and staff to test for the virus before returning from winter break.

However, districts in major cities such as Cleveland, Milwaukee and Atlanta have temporarily gone remote.

In Chicago, union members criticized the district's response to the highly contagious omicron variant of the virus. In a release, the union argued that district officials "put the safety and vibrancy of our students and their educators in jeopardy." Union members said testing resources are inadequate, calling on the mayor's office to implement more safety measures to slow the spread of the virus.

Chicago Teachers Union President Jesse Sharkey told the Associated Press teachers don't want to return to in-person instruction until the current surge has subsided.

"We'd rather be in our classes teaching, we'd rather have the schools open. What we are saying though is that right now we're in the middle of a major surge, it is breaking all the records and hospitals are full," he said during a Wednesday morning news conference with other union officials, teachers and parents.

But CPS officials fought back, saying the decision was unnecessary and disruptive to some families.

"Nobody signs up for being a home-schooler at the last minute," Chicago Mayor Lori Lightfoot said in a press conference before the vote, calling the action an illegal work stoppage. "We can't forget about how disruptive that remote process is to individual parents who have to work, who can't afford the luxury of staying home."

The union's vote comes as Covid infections hit all-time highs in Chicago. The city's health department on Tuesday said Chicago was averaging more than 4,000 new cases per day. Hospitalizations were also up slightly from the prior week.

Since late August, nearly 5,000 students have tested positive for the virus, according to CPS. During the same period, 1,802 adult school employees also reported cases. The highest week for positive cases among students and adults was in December, according to data provided by the district.

The Associated Press contributed to this report.