Twenty-two states and a number of large urban school districts — including the nation's largest in New York City and its second-largest in Los Angeles — are shutting down all K-12 schools as part of a sweeping attempt to contain the spread of the coronavirus.

Alabama, Alaska, Arizona, Arkansas, Delaware, Florida, Kentucky, Illinois, Iowa, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Montana, Nevada, New Hampshire, New Mexico, North Carolina, North Dakota, Ohio, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Utah, Vermont, Virginia, West Virginia, Washington and Wisconsin have made plans to close all schools.

Other major metropolitan districts such as Atlanta, Denver, San Francisco, San Diego, Washington, D.C. and Austin, Texas, have also shuttered. And a growing number of smaller districts around the country have also chosen to close.

The actions are the first wave of widespread school closings in the U.S., and they stand to upend school and family routines for millions of children. According to a count updated mid-afternoon Friday by Education Week magazine, about a quarter of American schoolchildren had been or were scheduled to be affected by a school closure — and that was before some states announced their actions.

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Such closures will throw into sharp relief the deep socioeconomic divides in American education. Disadvantaged families who rely the most on schools for stable services, such as meals and access to learning materials, will be some of the most negatively affected.

“Wide-scale learning loss could be among the biggest impacts coronavirus has on children in America,” said Betsy Zorio, vice president of U.S. programs at Save the Children, an international children's charity. “With an unprecedented number of school closures already announced and many more expected, ensuring that children can continue to learn is essential.”

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The effects on children will be particularly acute in places like Los Angeles, where the school district serves more than 600,000 students. Roughly 80 percent of students there rely on their school for lunch. More than 20,000 are homeless.

Ohio Gov. Mike DeWine kicked off the wave of statewide closures Thursday when he announced that all K-12 public, charter and private schools in Ohio will be shut down for three weeks starting Monday to try to contain the spread of the virus.

Shortly after the Ohio announcement, Maryland's superintendent announced the state's schools would close for two weeks starting Monday. Other states followed, most closing for two or three weeks. In Washington, the first state to have an outbreak spreading in the community, Gov. Jay Inslee ordered all schools closed by Tuesday through April 24 — about six weeks.

Some state leaders are still leaving the decision to close schools up to individual districts. Texas Gov. Greg Abbott declared a state disaster Friday, but stopped short of ordering a statewide shutdown of schools — despite 38 confirmed cases of the virus.

DeWine said the goal of the closures in Ohio is to slow the spread of the disease so that hospitals don't become overwhelmed. The virus has not sickened children as readily as older adults, but there is some concern that children could transmit the virus even if they have mild symptoms or no symptoms.

DeWine said he knows the closures will be unwelcome and disruptive news for parents statewide.

"We have compassion for that,” DeWine said. “But we have a responsibility to save lives."

Coronavirus school closures affect more than 25 million children

By Saturday evening, at least 57,000 schools across the country had closed or were planning to close since the outbreak began in the U.S., affecting more than 25 million children, according to the latest count by Education Week magazine. That's nearly half of the schoolchildren in America.

Confirmed cases of the infection in the U.S. surpassed 3,200 on Sunday, according to the Johns Hopkins University coronavirus data dashboard. So far, no children in the U.S. have died from the virus.

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The CDC has advised schools that if an infection is detected in the community, school leaders should consult with their local health departments about when to close, but should take steps to keep students spread out from each other, such as staggering dismissals, spreading out desks and canceling field trips. Schools should close at least for a few days in the case of an infected person who has been in the building, the CDC said in updated guidelines Thursday.

But as the virus has spread this week, school and political leaders have taken more aggressive actions.

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School districts facing an imminent shut down will have to figure out whether they will continue meal service for low-income families, whether they'll offer any sort of online instruction, and whether they'll have to change or cancel federally mandated state exams, which are often administered in spring.

"Over 20 million kids in the U.S. are eligible for free and reduced-price lunches, and school closures run the risk of depriving kids access to that," said Aaron Pallas, professor of sociology and education at Teachers College in New York City.

Illinois' governor shut down schools late Friday for two weeks, although Chicago Mayor Lori Lightfoot had said that doing so would have "cascading consequences." Chicago Public Schools, the nation's third-largest district, had closed just one high school and ordered a two-week at-home quarantine for students there, after an aide working at the school tested positive for the virus. During the Illinois closure, school staff plan to provide free food boxes with three days' worth of breakfast and lunches for families to pick up daily outside schools.

In Los Angeles, the district is closing schools for two weeks starting Monday, but plans to open 40 family resource centers starting Wednesday to provide child care for families that need it. All children will go home with a plan for lessons, Superintendent Austin Beutner said in a phone message to parents Friday.

"Los Angeles Unified serves a high-needs population, and our schools provide a social safety net for our children. The closing of any school has real consequences beyond the loss of instructional time," Beutner said. "These next few weeks will be difficult, and we're not certain what lies ahead after that."

Schools in New York City and in Nassau and Suffolk counties in New York will be closed starting on Monday. The 44 districts in Westchester County, the New York's epicenter for the coronavirus, are expected to announce they will also close for two weeks on Wednesday.

"Closing the schools is a good idea," New York Gov. Andrew Cuomo said during a Sunday conference call with county executives from Nassau, Suffolk and Westchester counties.

New York City Public Schools won't reopen until at least April 20, but could also be closed for the entire year, Mayor Bill de Blasio said.

The District of Columbia Public Schools announced Friday that while schools will close from Monday through March 31, students will participate in distance learning starting March 24. The district, which enrolls about 48,000 students, also said that meals would be available to students every day at sites across the district.

The federal government has said that schools can deliver meals in the community during the health crisis similar to how many districts distribute them in summer. But that they do not have to be handed out at a group site, officials said, as doing so would fly in the face of health experts' recommendations for "social distancing."

The Department of Education on Thursday announced it would allow states to apply for a one-year waiver from administering state exams in the event a prolonged closure interfered with their testing windows.

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Meanwhile, millions of families will have to figure out how to alter child care and work routines.

"It's especially hard for families of working parents who don't have jobs that provide the capacity to work remotely," Pallas added. "Young kids do need supervision, and we don't have a great backup system for the schools and for child care."

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Some individual schools and small districts have mobilized quickly to make a plan for delivering instruction online during a shutdown. But many larger districts, as well as those with many parents lacking access to technology, do not have the same capacity to do that.

After the closure announcements Thursday, many parents complained on social media, saying that shuttering schools would put additional pressures on parents, including putting some people's jobs at risk.

Pallas said he could understand how the extraordinary circumstances prompted such decisions.

"If kids learn anything during these breaks, it will be surprising," he said.

Contributing: Jackie Borchardt and Jessie Balmert, The Cincinnati Enquirer

Education coverage at USA TODAY is made possible in part by a grant from the Bill & Melinda Gates Foundation. The Gates Foundation does not provide editorial input.