The federal government issued new guidance Friday suggesting schools closed since the pandemic erupted could safely reopen at higher infection rates than California allows, and without necessarily vaccinating teachers first.

The guidelines from the Centers for Disease Control and Prevention come amid a furious national debate over reopening schools — many of which have been closed since last March. The backlash from some parents has been particularly fierce in California, which has been slower to reopen than other states.

The issue has pitted parents alarmed over the educational and emotional toll on their kids from prolonged online “distance learning” — widely acknowledged as inferior to in-person instruction — against other moms and dads and unionized teachers who fear infections remain too rampant to risk a return to classrooms.

“As a parent myself, I understand this is one of the hardest decisions you’ve had to make throughout the pandemic about the most precious thing you have,” said CDC Director Dr. Rochelle P. Walensky. “I want to assure you our strategy is science-based.”

The CDC guidance suggests that elementary schools, whose pupils are less susceptible to the coronavirus and easier to manage with typically one teacher and classroom, can reopen for partial in-person “hybrid” instruction even if the area where the school is located has relatively high virus transmission rates — and sets no bar at which schools could not do any in-person instruction.

The California Department of Public Health had no immediate comment on the CDC’s latest guidance.

Walensky said five widely adopted mitigation measures are key for safely bring students back: universal and proper face mask wearing by students, teachers and staff; physical distancing to keep kids six feet apart; handwashing and covering coughs and sneezes; cleaning surfaces; and promptly notifying and isolating those exposed to the virus. Of those measures, mask wearing and distancing were the most critical, Walensky said.

She strongly encouraged states to prioritize teachers and other school staff for vaccinations. But while that will help, she said, it isn’t needed to reopen classrooms.

“Science has shown that schools can reopen safely prior to teachers being vaccinated,” Walensky said.

In a report last month, the CDC said as of December, 62% of U.S. K-12 school districts were either fully open or offering a hybrid mix of online and in-person learning. Outbreaks have been “limited,” and COVID-19 infections in counties where K-12 schools offer in-person education were similar to that in counties offering only online education, the CDC reported.

Information about the open or closed status of schools statewide and around the country has been limited. Donna Harris-Aikens, senior policy advisor at the U.S. Department of Education, said that’s something President Biden’s administration aims to change.

“It is critical we learn how students are learning and the status of reopening,” Harris-Aikens said.

California officials Friday published online interactive maps promised a month ago showing the reopening status of public school districts and charter and private schools. A Bay Area News Group analysis this week found Bay Area public schools that have reopened for some form of in-class learning are overwhelmingly within the wealthiest districts.

Gov. Gavin Newsom has also been advocating for schools to reopen when it’s safe, although his approach has been less aggressive than what the CDC announced Friday. In December he unveiled a $2 billion “Safe Schools for All Plan” aimed at spurring schools to reopen as soon as this month, easing virus transmission criteria for opening elementary schools and offering new aid and guidance.

But big city school superintendents, teachers unions and many lawmakers balked, saying it didn’t meet their needs. School administrators said its requirements for testing students and staff were onerous, and teachers unions said either infection rates must fall much farther or they need to be vaccinated before returning in person. Newsom and state lawmakers have been in talks to hammer out a revised plan.

Some California counties are already moving to inoculate teachers. San Mateo County announced Thursday that it would begin vaccinating teachers on Feb. 22, as supply allows, and Sacramento will begin offering shots to educators beginning Tuesday, according to the Sacramento Bee.

Claudia Briggs, spokeswoman for the California Teachers Association, said, “What we have seen quickly is encouraging, but it’s a first step.” She added that teachers were glad to hear Walensky “strongly encourage states to prioritize teachers and other school staff to get vaccinated.”

But she and others cast doubt on the science indicating it’s safe, citing concerns about worrisome new and more transmissible virus strains. In a Friday press conference, the CTA included parents from inner-city districts where infection rates are high who said they don’t want schools to reopen.

“Folks who want our schools to be reopened, many of those families are more financially stable and live in areas where infection rates are much lower,” said Maria Osorio, a mother of four in Los Angeles, through an interpreter.

But some other parents told the Bay Area News Group that kids need to get back to the classroom.

“Other states and districts are open and have protocols in place to keep the staff and children safe,” said Laura Jimenez, a health care worker who pulled her two daughters out of public school in Brentwood and enrolled them in a private school that is open.