SAN RAFAEL (CBS SF) – With the school year underway, health officials in Marin County urged students and their families, along with staff, to wear masks on campus, both indoors and outdoors.

The Marin County Office of Education, along with Marin County Public Health, issued the recommendation Thursday amid rising COVID-19 cases and with students under 12 still not eligible to be vaccinated.

“With the Delta variant circulating in the community, universal masking is an added layer of protection for the entire school community,” the agencies said in a statement.

Officials cited recommendations by the American Academy of Pediatrics which urged universal masking on school campuses. The Centers for Disease Control has urged masking inside classrooms for all and for those not fully vaccinated to mask outdoors “in crowded outdoor settings or during activities that involve sustained close contact with other people” such as school playgrounds.

“We’ve risen to challenges before by following the guidance and using common sense. Face covering is among the easiest and most effective tools we have,” said Marin Health Officer Dr. Matt Willis.

While many Bay Area school districts were in distance learning for much of last year, Marin become one of the first counties in California to reopen all schools to some form of in-person learning during the 2020-21 school year. Only 19 cases of suspected in-school transmission of COVID-19 occurred out of more than 2.8 million student days recorded.

Officials credit the success in slowing the spread of the virus in schools with strong leadership in public health along with successful implementation of precautionary measures.

Earlier this month, Marin joined health departments in other Bay Area counties by again requiring masks at indoor public places, regardless of vaccination status, due to rising cases driven by the Delta variant.