President Joe Biden on Sunday said it was necessary for kids to return "safely" to school and to expect the Center for Disease Control and Prevention (CDC) to release "science-based" guidelines later this week on requirements for schools to reopen amid the ongoing pandemic

The president’s comments came during a pre-Super Bowl interview on "CBS Evening News." Asked by anchor Norah O’Donnell whether some 20 million American children having not been in the classroom for nearly a year – and the mental health damage that has caused – constituted a "national emergency," Biden said that it does.

The president said he thought it was time for schools to reopen "safely" under certain guidelines.

"You have to have fewer people in classrooms. You have to have ventilation systems that have been re-worked," Biden said. "Our CDC commissioner is going to be coming out with science-based judgement within I think as early as Wednesday to lay out what the minimum requirements are."

FILE: President Joe Biden speaks about the economy in the State Dinning Room of the White House in Washington. 

FILE: President Joe Biden speaks about the economy in the State Dinning Room of the White House in Washington.  (AP)

The president failed to mention, however, that CDC guidelines on schools reopening have been available for months. In mid-September -- nearly two months before the 2020 presidential election -- the agency released "Indicators for School Decision-Making."

The recommendations created a five-tiered risk assessment based on the number of new cases per 100,000 persons within the previous 14 days, and the percentage of positivity rates in the same timeframe.

The CDC said that a school falling into a "medium," "higher," or "highest," risk category did not necessarily mean that the school shouldn’t reopen for in-person learning, only that the school should use "alternative learning models" like a hybrid learning.

Last month, the federal agency said in a report that there is "little evidence that schools have contributed meaningfully to increased community transmission."

And last week, CDC Director Rochelle Walensky told reporters at a press conference: "there is increasing data to suggest that schools can safely reopen and that safe reopening does not suggest that teachers need to be vaccinated in order to reopen safely. Vaccination of teachers is not a prerequisite for the safe reopening of schools."

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Asked Thursday to respond to Walensky’s comments, White House press secretary Jen Psaki said the CDC Director was speaking "in her personal capacity."

"Obviously, she's the head of the CDC. But we're going to wait for the final guidance to come out so we can use that as a guide for schools around the country," Psaki said. "[Biden] believes that even with vaccinations for teachers or for any American, that there are a number of other mitigation steps that are important to take ... the wearing of masks, social distancing, ventilation, these are all factors that are important for... the reopening of schools."

Biden has pledged to reopen most of the nation's K-8 schools within his first 100 days in office, a goal he says is possible if Congress approves his pandemic rescue plan and if states prioritize teachers in vaccine rollouts. But the plan has drawn fire from critics who say Biden is cowing to teachers unions who helped him get elected.

Both of the nation's two major teachers unions endorsed Biden for president, including the National Education Association.

Some on the left have issued similar rebukes, including former New York Mayor and Democratic presidential candidate Mike Bloomberg, who said on MSNBC that Biden must "stand up" to teachers unions and force a return to the classroom.

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During a Fox News appearance on Sunday, Rep. Ronny Jackson, R-Texas, denounced teachers unions, which he claimed "essential owns" the Biden administration.

"This is just because of the influence, the political influence that the teachers union has on the Democrat Party," Jackson said. "They are just a large partisan pack. And as far as I’m concerned, they are really the worst of the worst as far as public unions go because of the way that they get that they control the Democrats."

The Associated Press contributed to this report.