Health officials now say that students who are masked can safely sit three feet apart, rather than six feet. The guidance applies to elementary, middle, and high schools.

It’s a fairly rapid change for the CDC. Just last month, it issued guidelines urging six feet of separation and suggesting schools limit the number of students in the building. Critics, though, felt that was overly cautious.

The revised guidance comes with an asterisk. The CDC says in communities where COVID-19 transmissions are still high, middle and high school students should maintain a minimum six-foot distance from each other. (Elementary school students have proved to be a lower risk for spreading the virus, said the CDC.)

And adults, the CDC underlined, should continue to remain six feet apart from one another and from students.

Still, the closer spacing guidance could accelerate plans to reopen schools, a priority for President Biden.

“CDC is committed to leading with science and updating our guidance as new evidence emerges,” said CDC Director Dr. Rochelle Walensky in a statement. “These updated recommendations provide the evidence-based road map to help schools reopen safely, and remain open for in-person instruction.”

While some groups might welcome the revision, the American Federation of Teachers is less likely to endorse schools reopening soon. Randi Weingarten, president of the union, recently said she worried the debate about reducing distancing requirements was “a debate about convenience, not a debate about safety.”