Chicago Mayor Lori Lightfoot deserves credit for standing up to the Chicago Teachers Union. But the fact that so many Chicago teachers were willing to abandon their students in the first place is disgraceful. The next time they walk off the job in violation of the law, she shouldn’t negotiate with them — she should fire them.

It is appalling that nearly three-quarters of Chicago Teachers Union members voted to walk out, locking more than 300,000 students out of their schools. As Lightfoot made clear, their actions were not only illegal, they were an attack on the well-being of Chicago children. “They abandoned their posts, and they abandoned kids and their families,” Lightfoot said this weekend.

She is right. They walked out even after they were allowed to cut the vaccination line and Congress appropriated $128 billion in President Biden’s covid-relief package to reopen schools. That’s nearly $2,500 per student nationwide. But it wasn’t enough. How is it that grocery clerks showed up for work throughout the pandemic — even before vaccines were available — but teachers refused to do the same? Apparently, grocery clerks believe they are essential workers, while Chicago’s teachers do not.

Early in the pandemic, we shut down schools because children are usually the most vulnerable to a contagion. But we now know that for kids, covid is no more dangerous than the flu. In Germany, not a single healthy child aged 5 to 17 died of covid between March 2020 and May 2021. Zero. We don’t know whether any healthy children died in the U.S. — because, incredibly, the Centers for Disease Control and Prevention does not track that information. But the fact is kids are safer in the classroom than they are at home — or even on the car ride to school.

By contrast, we know that school closures do irreparable harm to children. The American Academy of Pediatrics recently declared a pandemic-induced national state of emergency for children’s mental health. The CDC reports that the number of emergency room visits for suspected suicide attempts by girls ages 12 to 17 rose by 51 percent from early 2019 to 2021. School closures isolate children and rob them of their daily routines and interactions — lunches with friends, clubs, sports, plays and school trips. The damage is especially profound for poor children from broken homes. For kids with abusive or absent parents, school was their refuge — the one place where they experienced the support of caring and present adults. When schools close, they are abandoned by their teachers as well.