WASHINGTON (Nexstar) — About 70% of adults 18-and-over have now received at least one dose of the COVID-19 vaccine. But that’s not the case for students who are heading back to in-person classes this fall, and there is concern about the delta variant and low vaccination rates among eligible students.

Mary Wall, a senior policy adviser for the White House COVID-19 response team, said the vaccination rate among students is “still in the high 30% for age 12 to 15 nationwide, and for age 16 to 17 it’s in the high 40s.”

That’s why she said it’s important for schools around the country to follow the guidance from the CDC and education department — “universal masking for everyone in schools, students and teachers and staff,” Wall said.

School districts around the country are grappling with whether to implement vaccine and mask mandates, knowing that no matter what they choose it will upset some parents.

Health officials stress the guidance will save lives “so our children can safely get back to school and safely stay there,” said CDC Director Dr. Rochelle Walensky.

But officials said the federal government is not planning a mask or vaccine mandate in schools.

“We think that this is a matter that’s best left to states and local school districts to figure out, as is currently the policy for all vaccines,” Wall said.

She said the Biden administration is helping to drive up voluntary vaccine rates among students. President Biden asked all school districts to host vaccine clinics at schools to make vaccines more accessible to students and staff.