Biden to GOP governors threatening to sue over vaccine mandates: 'Have at it'

President Joe Biden and first lady Jill Biden visited a local middle school in Washington on Friday to talk about keeping students safe in classrooms as the raging delta variant has upended the start of the school year -- and one day after Biden took his toughest tone yet and announced sweeping new federal requirements for vaccines and testing.

But Biden also offered another lesson to the next generation when asked by ABC News Congressional Correspondent Rachel Scott about Republican governors calling his call for vaccination mandates an "overreach" and threatening to sue the federal government over his new plan.

"Have at it," Biden said.

"I am so disappointed that particularly some Republican governors have been so cavalier with the health of these kids, so cavalier with the health of their communities," he said following brief remarks on keeping schools safe.

"One of the lessons I hope our students could unlearn is that politics doesn't have to be this way," he said. "They're growing up in an environment where they see it's like, like a war, like a bitter feud...It's not who we are as a nation. And it's not how we beat every other crisis in our history."

Reintroducing his six-part strategy to combat the pandemic, Biden focused his remarks at Brookland Middle School on how his approach will help keep schools safe, including requiring that 300,000 educators in federal Head Start programs be vaccinated and using the Defense Production Act to produce nearly 300 million rapid COVID-19 tests for distribution at the schools around the country.

He also called for more governors and school districts to implement vaccine requirements.

"We all know if schools follow the science -- like they are here -- and implement safety measures like vaccinations testing, masking, then children can be safe in schools safe from COVID-19," he said.

Biden acknowledged the Food and Drug Administration has not yet approved vaccines for children under 12, leaving a large swath of the population without the choice to be vaccinated. He said while the FDA is working on the science "as safely and as quickly as possible," the onus is on children aged 12 to 17, and adults, to get the shot to keep schools open.

"The safest thing you can do for your child 12 and over is get them vaccinated," Biden said, speaking directly to parents.

He reminded that vaccine requirements in schools are "nothing new."

"You got them vaccinated for all kinds of other things -- measles, mumps, rubella -- for them to go to school, to be able to play sports, they've had to have those vaccinations," he added. "It is safe, and it's convenient, and we'll work to bring the vaccine clinics to our schools as well."

Praising local vaccine incentives already in play, Biden, seemingly going off script, also offered the students at Brooklyn Middle School a visit to the White House once they're all vaccinated.

"I'm going to get in trouble with the Secret Service and everybody else. I'm not sure how we're going to mechanically do it, but I assume the buses can get you to the White House and if we can't get you all in one room. We'll be out in the Rose Garden or out in the back there and maybe let you fly the helicopter," Biden said to laughter. "I'm only joking about that."

The first lady, who returned to teaching this week and has been an advocate for keeping kids in the classroom, speaking ahead of her husband said it was the responsibility of educators and families to make schools safe for kids.

"We owe them a promise to keep their schools open as safe as possible. We owe them a commitment to follow the science. We owe them unity, so that we can fight the virus, not each other as we move forward," she said.

In his address to the nation on Thursday, Biden also promised to make up the salary of any teacher or administrator whose pay was withheld for opposing state bans on masks.

Ahead of their remarks, the Bidens visited the classroom 6th-grade science teacher Ms. Michelle Taylor and talked with students, all of whom were masked up.

The visit comes after a record-high 2,396 children were hospitalized with COVID-19 as of Tuesday. In the last week alone, nearly 252,000 children in the U.S. have tested positive for COVID-19, marking the largest increase of pediatric cases in a week since the pandemic began, according to a newly released weekly report from the American Academy of Pediatrics and the Children's Hospital Association.

ABC News' Arielle Mitropoulos contributed to this report.