Chicago Teachers Union members may strike if their demands for negative coronavirus tests for all students to return to class after winter break — or a two-week return to remote learning — are not met.

More than 90% of CTU members voted in favor of participating in "a remote-work action" as soon as "the first week" after winter break if CPS "doesn't call for a period of remote instruction after winter break," according to a Wednesday news release from CTU President Jesse Sharkey.

The union on Thursday presented Chicago Public Schools (CPS) with a proposal demanding COVID-19 protections, which include a "massive increase in testing" and negative COVID tests "in order for all students to return to class," or a two-week return to remote learning, an email from Sharkey to union members reads.

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"At this point, it is up to us — all of us in solidarity — to ensure safety for our members, our students and our school communities," Sharkey said in the email. "…Safety committees are the authority on safety in our schools. We can use them to take back control from our principals and CPS. But we need to organize in our buildings to prepare members for action if and when concerns are ignored."

Sharkey is encouraging schools' safety committee members, which are composed of CTU members, to "engage in remote-only work until your safety concerns are met, like members at Carnegie did earlier this month after a staff member died from COVID."

Students are escorted from Hawthorne Scholastic Academy to meet their parents following their first day of in-person learning on March 01, 2021 in Chicago, Illinois. (Photo by Scott Olson/Getty Images)

Students are escorted from Hawthorne Scholastic Academy to meet their parents following their first day of in-person learning on March 01, 2021 in Chicago, Illinois. (Photo by Scott Olson/Getty Images)

It may be illegal for union members to strike under the Illinois Educational Labor Relations Act if "mediation has been requested by the union but not completed; the union hasn’t given the employer an official notice of intent to strike or 10 days’ notice; and there is a collective bargaining agreement in place," according to nonprofit advocacy organization Illinois Policy.

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CTU members have gone on strike several times throughout the past decade. Ahead of a planned strike last January, CPS CEO Janice Jackson told NBC Chicago that teachers on strike would be "deemed absent without leave" and would "not be eligible for pay going forward."

 Corey DeAngelis, national director of research at School Choice Now, criticized the move in a statement to Fox News.

"The union should just be honest about what they're getting ready to do. It's a strike," he said. "They're being deceptive by calling it ‘a remote work action’ or a ‘schoolwide operational pause.’ If employees are expected to show up to work in person and they don't, that is a strike, not a ‘remote work action.’"

Chicago Teachers Union leadership list their demands and leave a box of coal outside the entrance of City Hall on January 4th, 2021. (Photo by Max Herman/NurPhoto via Getty Images)

Chicago Teachers Union leadership list their demands and leave a box of coal outside the entrance of City Hall on January 4th, 2021. (Photo by Max Herman/NurPhoto via Getty Images) (Getty Images)

DeAngelis believes that if grocery store employees strike, "families can take their money elsewhere," but "if public school employees strike, families should be able to take their children's education dollars elsewhere."

The union will discuss its proposal during a Sunday town hall, which is being held the day before CPS returns to school from winter break on Jan. 3.

Earlier this year, the union engaged in a school reopening dispute with the city that got increasingly bitter before both sides came to an agreement.  

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"In January, members voted overwhelmingly not to return to buildings and to continue teaching remotely until a safety agreement was in place. Courageous educators across the city braved frigid temperatures — and potential disciplinary action — teaching outside as the mayor tried to force students, educators and staff back into unsafe school buildings," the Union wrote in a year in review article on its website. "The vast majority of families refused and stuck with remote learning for the rest of the school year." 

Chicago recorded a daily rate of 145.6 positive COVID-19 cases per 100,000 people this week — a 42% increase compared to last week as the omicron variant continues to spread across the U.S.

Despite the high positivity rate, however, deaths remain relatively low. Chicago recorded 3.6 hospitalizations and 0.4 deaths per 100,000 people. There have been an average of 3,940 positive cases and 10 deaths per day as of Dec. 30.

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While positive cases have surged to their highest rate since the beginning of the pandemic in Chicago, deaths are significantly lower than they were during the last surges in May and December 2020 as the majority of Chicago residents get vaccinated. More than 64% of Chicagoans have received both COVID-19 vaccine doses.

Fox News' Greg Norman contributed to this report.