(NewsNation Now) — Schools around the country are dealing with another surge of COVID-19, fueled this time by the omicron variant, and mayors in cities including Chicago and New York are doing everything they can to keep schools open for in-person learning.

“The safest place for children is in a school building,” said New York City Mayor Eric Adams on CNN’s “State of the Union.” “And what we want to do is not get in the way of preventing children from coming into that building.”

Adams, a Democrat who was sworn into office Jan. 1, is holding his promise to a pledge to keep kids in school.

“I need my children in school, and any barrier to do that, I believe, is more harmful than helpful,” he said.

In Chicago, the nation’s third-largest school district, the standoff between Chicago Public Schools and the teachers union continues. Monday will mark the fourth straight day without a return to in-person learning. The teachers union voted against a return to the classroom last Tuesday due to rising COVID cases and safety concerns.

“What the Chicago Teachers Union did was an illegal walkout,” said Chicago Mayor Lori Light on NBC’s “Meet the Press” on Sunday. “They abandoned their posts and they abandoned families.”

According to Burbio, a tech company that tracks school disruptions, more than 5,400 schools nationwide were without in-person learning last week. Lightfoot said the conflict between the union and the city is hurting children. She said many of them are in financially unstable situations at home and need to be in the classroom.

“What we cannot do is abandon the science,” she said. “We know that the safest place for our kids to be is in-person learning in schools.”

CDC director Dr. Rochelle Walensky agreed, saying Sunday that classrooms are safer now than earlier in the pandemic.

“We had a delta surge and we were able to safely keep our kids in school before we had pediatric vaccination,” Walesnky told Fox News on Sunday. “Fast forward to now; we have pediatric vaccinations.”

Education Secretary Miguel Cardona, who joined NewsNation’s “Rush Hour” on Thursday, echoed Dr. Walesnky saying, “students suffered enough” and schools should stay open.

“I know we have the tools to get our school safely open,” Cardona said. “And we have to do everything in our power to give our students the best opportunity for success. And that means giving them an in-person learning opportunity.”