Long after the rest of the country ditched their masks and went back to some semblance of normality, officials in a handful of school districts across the country have reinstated mask mandates for students for the upcoming school year.

After declaring masks optional a month ago for the first time since the pandemic began, officials with Prince George County Schools outside of Washington, D.C., reversed themselves on Friday and said they would be required indoors effective Monday. The school district in Maryland said it took the action based on the advice of the county health department.

“Mask policy is subject to change according to local and/or state health department guidelines and Centers for Disease Control and Prevention recommendations,” the district said in its announcement.

In Philadelphia, school officials said masks would be required for all students and faculty for the first two weeks of the school year, which begins on August 29. After that, it said, masks would be optional but strongly encouraged.

Students and staff in all of Philadelphia’s federally funded Head Start pre-kindergarten programs — which typically serve students between the ages of 3 and 4 years — will be required to wear masks indoors for the entirety of the school year, the district said.

A widely watched survey of school mask mandates reports that 97 percent of the 500 largest school districts in the country have relaxed their rules for the coming school year. There are still eight holdouts with mandatory mask requirements, however, and seven more that have partial mandates, ranging from the districts in Maryland and Pennsylvania to smaller districts in Kentucky, Wisconsin, Connecticut, and Texas.

There are no more statewide mask mandates in place in America.

Last week, the Centers for Disease Control issued new Covid guidance taking into account the “stronger place” the country finds itself. The guidance eliminated so-called test-to-stay edicts that required those exposed to the virus to test regularly in order to remain in school. The guidance also dropped recommendations that exposed unvaccinated students to quarantine and social distancing rules.

The CDC’s latest advice on masks is that schools take into account risks at the community level when deciding whether to enforce mask mandates. The agency stressed that schools try to accommodate both students who choose to wear marks and those who do not.

“Schools and ECE programs should consider flexible, non-punitive policies and practices to support individuals who choose to wear masks regardless of the COVID-19 Community Level,” the guidance stated.

According to the CDC, roughly three-quarters of American children have had Covid, and that data was from before the surge of more transmissible omicron subvariants. By now, the agency has estimated, most children — as well as most of the general population — are protected from the virus as a result of vaccination, prior illness, or both.

So why are schools still forcing the least vulnerable members of a mostly protected population to follow mask mandates? Officials in Prince George County issued their three-paragraph rule with no further comment, other than to say that it was at the behest of county officials and “in light of the highly contagious COVID-19 BA.5 variant.”

At a news conference announcing their policy, school officials in Philadelphia also said their decision is based on advice from county health officials and the CDC. Philadelphia is currently facing a “medium” threat, with an average of 260 new cases daily out of a population of 1.5 million.

The district’s chief medical officer, Dr. Kendra McDowell, said the district may change its rules at any time based on the level of community transmission. The logic behind the first-10-days mandate, she said, is that students are just returning from summer vacation.

“This is an extra precaution for everyone’s health and well being since increased end-of-summer social gatherings may heighten the risk of exposure to Covid-19,” Dr. McDowell said.