All U.S. students, teachers and staff should wear masks when in school, regardless of their vaccination status, the American Academy of Pediatrics (AAP) said Monday.

That guidance runs counter to recommendations released by the U.S. Centers for Disease Control and Prevention earlier this month: Those guidelines said teachers and students who are vaccinated can enter schools without masks, while the unvaccinated should continue to wear them to protect themselves against the coronavirus.

The CDC did not offer suggestions on how teachers can know which students are vaccinated or how parents will know which teachers are immunized. The biggest issues will be at middle schools where some students are eligible for shots and others are not. If sorting vaccinated and unvaccinated students proves too difficult, administrators might choose to just keep a masking policy in place for everyone, the CDC said at the time.

"Most of us don't really like wearing a mask. Let's just admit that," said Dr. Michael Grosso, chair of pediatrics Northwell Health's Huntington Hospital in Huntington, N.Y.

"But it is hard not to like the new guidance from the American Academy of Pediatrics. First, kids need to be back in school, face to face, and the AAP is promoting that. This is important for every child, and even more for children with learning problems. It's important for learning, for socialization, for physical fitness and for mental health," he said.

"Second, most schoolchildren are un-immunized, at least for now, and will remain that way until the studies are completed and we have authorization for the use of the vaccines in younger individuals," Grosso added. "This will take a little while longer. For now, un-immunized children need the protection that comes with masking everyone in the school setting."

Despite the fact that children are less likely than adults to get severe COVID, they are at risk for MIS-C, which affects about 1 in 600 infected children and teens, Grosso said. "This multi-system inflammatory condition, which follows primary infection by several weeks, is extremely serious, and more often than not results in the need for pediatric intensive care," he noted.

Along with recommending masking for all, the AAP's latest guidance says all eligible people should be vaccinated against COVID-19, strongly recommends in-person learning, and advises schools to prepare for students' mental health needs.

"We need to prioritize getting children back into schools alongside their friends and their teachers -- and we all play a role in making sure it happens safely," said Dr. Sonja O'Leary, chair of the AAP Council on School Health.

"The pandemic has taken a heartbreaking toll on children, and it's not just their education that has suffered but their mental, emotional and physical health," O'Leary said in an AAP news release. "Combining layers of protection that include vaccinations, masking and clean-hands hygiene will make in-person learning safe and possible for everyone."

Universal masking is necessary because a significant portion of students are not yet eligible for vaccines, and masking is proven to reduce transmission of the virus and to protect those who are not vaccinated, according to the AAP.

Also, many schools will not be able to monitor the vaccine status of students, teachers and staff, and the virus may be more widespread in communities with low vaccination rates.

"There are many children and others who cannot be vaccinated," said Dr. Sara Bode, chairperson elect of the AAP Council on School Health Executive Committee.

"This is why it's important to use every tool in our toolkit to safeguard children from COVID-19. Universal masking is one of those tools, and has been proven effective in protecting people against other respiratory diseases, as well," Bode said in the release. "It's also the most effective strategy to create consistent messages and expectations among students without the added burden of needing to monitor everyone's vaccination status."

The AAP guidance does echo CDC recommendations for school building ventilation, testing, quarantining, cleaning and disinfection.

Safety precautions are highly effective when used consistently, and children are at higher risk of suffering mental health issues and developmental setbacks if they miss out on in-school learning, according to AAP.

It's also crucial that children are caught up on all regular vaccinations, including the flu shot, the AAP said.

"The last thing we want as we come out of this pandemic is an outbreak of another vaccine-preventable disease," O'Leary said.