Students should wear masks and practice social distancing at school to ensure safe in-person learning this fall, top U.S. doctors said Tuesday.

Just 30% of 12- to 17-year-olds are fully vaccinated in America, and younger kids won’t likely get the shots until well into the school year. That has the American Academy of Pediatrics and other top doctors worried that the delta variant could rip through U.S. schools when kids return to the classroom this fall.

“I do think that mask mandates or universal masking in the school setting should be enforced … there are still a lot of very susceptible individuals that will be attending school in person,” Dr. Tina Tan, professor of pediatrics at Northwestern University, said on a call Tuesday hosted by the Infectious Diseases Society of America.

Tan also said that there are many teachers and school staff remain unvaccinated, “and one way to really protect these individuals against getting Covid in the school setting would be to enforce a mask mandate until a higher percentage of these individuals can be vaccinated.”

For children under 12 who are unable to get vaccinated, “you’re going to have to resort to the protective mitigation protocols that we used prior to the availability of vaccine until these individuals become eligible for vaccination,” Tan said.

Their call for masks in schools comes as the Centers for Disease Control and Prevention is poised to announce new indoor mask guidelines for fully vaccinated people on Tuesday.

The CDC in May eased its mask guidance for kids in summer camp, saying at the time that fully vaccinated kids didn’t need them.

Vaccine eligibility for children under 12 years old could come as soon as the end of this year, or the early half of 2022, vaccine makers have predicted.

To reduce the spread of Covid this fall, schools could keep desks at least three feet apart and teachers could be assigned smaller class sizes, experts say.

Returning to in-person learning is important for kids too, “given the significant negative impacts that have resulted from not attending school in person over this past year,” said Tan.

Attending school online has resulted in lack of motivation, troubles for some kids and feelings of isolation in kids.

Nearly 25% of parents whose kids attending virtual school reported worsening mental or emotional health, compared to 16% of parents whose kids attended school in person, according to a CDC study.

The trend held for parents as well, 54% of parents with children enrolled in virtual learning reported emotional distress, compared to 37% of parents with children attending school in person.

Only about 27% of parents of children under age 12 say they will get their child vaccinated, according to Kaiser Family Foundation data. 27% say they will “definitely not” get their child vaccinated.

About half of parents surveyed in the KFF data say they’re worried about potential side effects of the vaccine.

“We need to do something beyond just saying ‘go get vaccinated,’ and I don’t know that the incentives have worked that well, but mandates do push people,” Dr. Preeti Malani, chief health officer at the University of Michigan, said on the call.

About 61% of parents of children under the age of 18 are not in favor of vaccine mandates in schools, according to Kaiser’s data.

With most school-age children unvaccinated, doctors say masking and social distancing remain the best options for in-person learning.

“If there are no mask mandates at the school or the school has made masks optional, you need to send your child to school with a mask,” Tan said.