Chicago Mayor Lori Lightfoot, D., continued her war of words with the city's teachers' union, telling MSNBC on Thursday that its holdout was "incredibly sad" as it was attempting to "politicize the pandemic."

As "Morning Joe" co-host Willie Geist noted more than 90 percent of the Chicago Teachers Union were vaccinated and children were being hurt, he asked Lightfoot how he viewed its members' vote to switch to remote learning, leading to two consecutive days of canceled classes in the country's third-largest school district.

"Well, unfortunately I think the only way to read it is the union trying to politicize the pandemic, which is really incredibly sad," she said.

Mayor Lori Lightfoot presides over a City Council meeting on Oct. 27, 2021, in Chicago. (Antonio Perez/Chicago Tribune/Tribune News Service via Getty Images)

Mayor Lori Lightfoot presides over a City Council meeting on Oct. 27, 2021, in Chicago. (Antonio Perez/Chicago Tribune/Tribune News Service via Getty Images) (Antonio Perez/Chicago Tribune/Tribune News Service via Getty Images)

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"What does that mean, Mayor Lightfoot? What do they get out of that?" Geist asked.

"What it gets is they get to try to flex their power, but they do it at the expense of our children," she said. "They do it at the expense of our families. We know that when we were fully remote previously, 100,000 of our kids lost contact and would disengage from the system. We saw in the elementary schools the failure rate during remote learning triple from what it was. We saw the trauma and social emotional harm to students across our system. 

"So this is about politics, it’s not about the pandemic … Fundamentally the absolute wrong thing to do right now is to abandon the science and data that tells us unequivocally that our schools in person are the best place for our students to be. So we’re drawing a line. Enough is enough. I’m tired of the Groundhog Day appearance of everything that goes on with the Chicago Teachers Union leadership. We need partnership, we don’t need conflict right now."

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Lightfoot announced on Wednesday that her office filed an unfair labor practices complaint after the city’s teachers union voted to switch to remote learning due to a surge in COVID-19 cases. 

CHICAGO, ILLINOIS - JANUARY 05: A sign on the fence outside of Lowell elementary school welcomes students on January 05, 2022 in Chicago, Illinois. Classes at all of Chicago public schools have been canceled today by the school district after the teacher's union voted to return to virtual learning, citing unsafe conditions in the schools as the Omicron variant of the coronavirus continues to spread.   (Photo by Scott Olson/Getty Images)

CHICAGO, ILLINOIS - JANUARY 05: A sign on the fence outside of Lowell elementary school welcomes students on January 05, 2022 in Chicago, Illinois. Classes at all of Chicago public schools have been canceled today by the school district after the teacher's union voted to return to virtual learning, citing unsafe conditions in the schools as the Omicron variant of the coronavirus continues to spread.   (Photo by Scott Olson/Getty Images) (Scott Olson/Getty Images)

Lightfoot told CBS Chicago that she hoped to come to an agreement at the bargaining table, not a courtroom. But she called the latest moves from the union an "illegal strike."

The Chicago school system announced Wednesday that classes were canceled for a second-straight day and parents were—once again—given just hours’ notice that there were no classes, Fox 32 reported.

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Fox News' Edmund DeMarche and the Associated Press contributed to this report.