CHICAGO — Chicago schools have canceled classes Wednesday after the teachers union voted to switch to remote learning due to record COVID-19 levels.

The move comes amid an escalating battle over safety protocols in schools.

Officials in the nation's third-largest school district say they won't switch back to online instruction districtwide, as it was devastating for children's learning and mental health. But the union says the district's safety protocols are lacking, and both teachers and students are vulnerable.

"Tonight, as educators, parents, neighbors and community members, we had to make the tough decision to support a resolution to return to remote learning in our city's public schools," the union said in a statement. "This decision was made with a heavy heart and a singular focus on student and community safety."

CNN reports that Chicago Public Schools called the union's vote an "unfortunate decision."

Both sides are negotiating metrics that would trigger school closures, among other things.

School officials say buildings would remain open for administrators and staff and essential services like meals for students. WMAQ-TV in Chicago says that all sporting events and extracurricular activities scheduled for Wednesday have also been canceled.

The status of class for the rest of the week was unknown.