The Centers for Disease Control and Prevention announced a long-awaited roadmap for opening the nation's schools on Friday, saying that in-person learning can be done safely amid the pandemic. The CDC strongly urges states to vaccinate teachers, although it's not a requirement for schools to reopen.
The guidance emphasizes masks, physical distancing and cleaning classrooms as ways to prevent the spread within schools. The CDC calls the guidance an "operational strategy" but it is not a mandate for schools to open or close.
"There is nothing in this guidance that is a mandate for schools to open, and nor is there anything in this guidance that is a mandate for schools to close," CDC director Dr. Rochelle Walensky told NBC News.
Instead, it's "very much a roadmap of — given the amount of disease in the community — what we believe are the next best steps to make sure that when you do open, or if you stay open, it's done so safely," Walensky said.
The latest guidance is based on science and outreach with teachers, parents and the Department of Education. CDC officials conducted comprehensive reviews of literature and extensively studied what happened during school openings in the fall and in Europe, Walensky said. Officials said there is strong evidence now that in-person schooling can be safe, especially at lower grade levels, and the guidance is targeted at schools that teach kindergarten up to 12th grade.
The agency also emphasized hand washing, disinfection of school facilities, diagnostic testing and contact tracing to find new infections and separate infected people from others in a school.
The guidance was issued as President Joe Biden faces increasing pressure to deliver on his promise to get the majority of schools back to in-person teaching by the end of his first 100 days in office. The White House said this week that a national strategy would be guided by science.
There's wide agreement that learning in the classroom is more effective and that students can face isolation and learning setbacks at home. But teachers unions in some areas say schools have failed to make buildings safe enough to return.
CDC officials emphasized that in-person learning has not been identified as a substantial driver of coronavirus spread in U.S. communities, and that transmission among students is now considered relatively rare.
The CDC also stressed that the safest way to open schools is by making sure there is as little disease in a community as possible. The agency urged local officials to assess whether a bad outbreak is occurring in a community when making decisions about sending adults and children in to schools.
"So much of getting back to school safely is really about how much disease is in the community, because most of what comes into the schools is coming in from the community," Walensky said.
The guidance included a color-coded chart, from blue to red, on assessing community spread, including rates of new cases per 100,000 people and the percentage of positive tests.
That said, high community transmission does not necessarily mean schools cannot be open — especially those at the elementary level. If school mitigation measures are strictly followed, the risk of spread in the schools should still be low, the guidance suggests.
The document suggests that when things get risky, elementary schools can go hybrid, providing in-person instruction at least on some days, but that middle and high schools might go virtual.
Biden has been caught between competing interests as he works to get students in the classroom without spurning the powerful teachers unions that helped get him elected. Critics say he has bowed to unions instead of taking more aggressive action on reopening.
Unlike former President Donald Trump, who pressured schools to open and blasted the CDC for issuing guidance that he said was impractical, Biden has kept his distance from the CDC as it works on recommendations. Even after the CDC's director recently said that vaccinations are not a prerequisite for reopening, the White House declined to take a firm stance on the question.
Getting students back in the classroom is seen as a key to getting parents back to work. As part of Biden's coronavirus relief package, he's calling for $130 billion to help schools update buildings, buy protective gear and enact other recommended safety measures.
Biden's national strategy says the administration "will also work with states and local school districts to support screening testing in schools, including working with states to ensure an adequate supply of test kits."
But the CDC guidance stops short of recommending testing, saying "Some schools may also elect to use screening testing as a strategy to identify cases and prevent secondary transmission."
Existing CDC guidelines encourage a variety of measures to fight COVID-19 in schools, including the use of masks in certain settings, along with social distancing, hand washing and regular cleaning.
The guidance is also personal for Walensky. The mother of three teenage boys, Walensky understands the difficulties parents face.
"It's been so hard," Walensky told NBC News. "I have one who missed half of his senior year of high school."
This story was originally published on NBCNews.com.