Chicago - Chicago Public Schools, the third-largest U.S. education district, will resume in-person classes on Wednesday after a teachers union backed ending a walkout over COVID-19 protection fears, the mayor and union leaders said on Monday.

Earlier, the union representing public school teachers had tweeted: "The Chicago Teachers Union House of Delegates has voted tonight to suspend the Union's remote work action while rank-and-file membership votes on the proposed agreement."

The walkout started last week, idling some 340,000 students, and came after the teachers’ union voted to reinstate virtual instruction and pushed for more rigorous safety protocols, including wider testing, citing the rapid spread of the highly infectious Omicron variant in recent weeks.

“We’re going to keep doing what’s right,” said Chicago Teachers Union President Jesse Sharkey during a news conference confirming the deal to return to classes.

The Chicago Teachers Union said Monday night that it expects to open polls Tuesday for rank-and-file members to vote on the agreement.

"This agreement moves toward what they have been asking for a long time even if it doesn't get all the way that we think we should have," CTU Chief of Staff Jen Johnson said.

This deal included agreement on the metrics involved for determining school closures, according to Lightfoot.

As of Friday, Chicago was averaging more than 5,200 new cases a day -- a 16% increase over the prior week, according to the city health department's Covid-19 tracker. The city's Covid-19 test positivity rate had a daily average of 21.1%.