The Chicago Teachers’ Union vows to fight a plan to end mandatory school masks.

Chicago Public Schools announced plans to lift the mask-wearing requirement in the U.S. third-largest school district starting next week, infuriating teachers’ union members who stopped showing up to school buildings for a week in January demanding more Covid-19 protection measures. 19.

The decision, announced on Monday, follows a legal battle in the Illinois courts over school masks, and recent moves by Gov. J. B. Pritzker and Mayor Lori Lightfoot to lift other virus regulations as cases plummeted. .

But teachers’ union officials vowed to file charges of unfair labor practices. They said the decision to lift the mandatory use of masks was premature, especially amid relatively low student vaccination rates, and said the breach of the agreement forced them back into the classroom earlier this year.

“Today’s move by Mayor Lightfoot and the CPS not only violates the union’s agreement with the district, but also ignores the impact Covid-19 is having on communities of color,” the Chicago Union of Teachers said in a statement. African American and Hispanic students make up over 80 percent of Chicago’s approximately 330,000 public school students.

An analysis of vaccination data by WBEZ, Chicago’s public radio station, found that in nearly 75 percent of the district’s schools, less than half of students were fully vaccinated as of February 22.

In Chicago and across the country, several issues related to the pandemic have been more contentious than whether to hold face-to-face classes and whether to require masks. Teachers in Chicago stopped showing up for class shortly after the winter break, during the biggest Omicron surge, claiming the schools were unsafe, and the controversy caused classes to be cancelled.

Back then, both the union and the county supported the mandatory wearing of masks. But Mr. Pritzker, a Democrat, last week lifted the mask order for schools across the state. And school district leaders said Chicago’s improved Covid situation made it wise to make masks optional in schools starting next Monday.

CPS was one of the first to require universal mask-wearing in schools, and we will not move to a no-mask model unless the data and our public health experts indicate it is safe for our school communities.” — Pedro Martinez, Head districts. executive branch,” the statement said.

Cook County, which includes Chicago, was averaging more than 11,000 new cases per day at the height of the labor dispute in January. The county is now averaging about 600 new cases daily, and hospital admissions have also fallen sharply. Last week, masks became optional at most other places in the city, and proof of vaccination is no longer required to dine indoors.

The school district is facing legal pressure to withdraw its mask mandate. The Chicago Tribune reported that Thomas DeVore, a lawyer who lives in Southern Illinois and is seeking the Republican nomination for state attorney general, filed a motion in state court last week asking a judge to block enforcement of a mask-wearing order in Chicago schools.