School closures rippled across the country in the wake of the new coronavirus, amounting to one of the most dramatic upheavals of American schooling in a century.

Over a dozen states, including Illinois, Michigan, Ohio, and Pennsylvania, have called school off for a week or more. The nation’s second-largest school district, Los Angeles, is also closed for at least two weeks. As of Friday evening, Education Week estimated that at least 40 percent of students nationwide have been affected by closures.

Holdouts, like leaders in New York City, are facing increased pressure to close schools in hopes of limiting the spread of COVID-19, the illness caused by the new coronavirus. In some schools that have stayed open, attendance has fallen sharply.

There remains debate on whether closures are warranted to stop the spread of the virus. So far, most confirmed cases have been among adults, and children who’ve tested positive for the virus have had milder symptoms. But they still may play a role in spreading it.

Guidance released today by the Centers for Disease Control and Prevention encouraged schools to close in certain circumstances, while acknowledging other countries’ experiences haven’t proved closures would slow the illness.

The guidance says that shorter school closures, of two to four weeks, had not clearly proven effective in limiting the coronavirus spread in other countries. Closures of eight weeks or more, the CDC said, could be more effective.

Meanwhile, congressional leaders and the Trump administration are attempting to iron out a response to the crisis, including efforts to cushion the blow of school closures. “Our legislation protects our children, in particular the tens of millions of little children who rely on the free or reduced-price lunch they receive at schools,” said House Speaker Nancy Pelosi. President Trump declared a state of emergency on Friday afternoon, and the House is expected to vote on a version of the coronavirus relief bill sometime Friday.

How long these school closures will last is difficult to predict, because much is unknown about the virus. “When you have an outbreak like this,” Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, said Friday, “it’s really impossible to predict the time element of when it’s going to peak and when it’s naturally going to go down.”

The CDC says while it has some data that can help communities decide when to close schools, “there is almost no available data on the right time to re-start schools.”

What is clear is that the mass closures of schools — particularly if they remain shuttered for many weeks — will create a series of cascading academic, economic, and social challenges. Here are some of them.

🔗Lost instruction

A key consequence: kids who aren’t in school aren’t getting instruction, at least not in the traditional way. Research suggests that closing schools for a few days probably won’t hurt students academically, but prolonged closures could affect students’ educational trajectories.

To avoid that, some districts have attempted to put in place “distance learning” structures — including computer programs, assignments sent home, and even a television channel in Los Angeles.

But this is difficult to pull off, and might exacerbate existing inequalities.

Virtual learning is much less effective than face-to-face instruction, studies have shown. Advocates for students with disabilities are particularly concerned. Guidance released by the Department of Education this week reiterated that schools attempting to deliver remote instruction must continue to serve students with disabilities.

“Sure, it could work for some kids, I just have my reservations on saying it’s going to work for all kids,” Jen Cole, who provides assistance to parents of students with disabilities through a Washington-based nonprofit, told Chalkbeat.

Some places, like Washington state, have discouraged schools from attempting distance learning at all. Districts that have tried going remote, like the Northshore School District in Washington, have already heard reports from parents who say their children are having a hard time staying focused.

🔗School meals

Over 30 million American children get meals from the National School Lunch Program. The U.S. Department of Agriculture, which administers the program, is offering flexibility for schools that want to continue to offer meals to students even while closed. (States currently must apply for waivers from certain rules, such as one that requires students to eat meals together — which would partially defeat the purpose of closing schools.)

For instance, districts can designate food pick-up locations, at schools or other locations like libraries. In New York City, officials are offering free “grab and go” meals to the handful of schools that have closed so far, offering food like canned fruit, hummus, and cereal. When all of Memphis’ schools closed this week, community agencies quickly began food drives. A guidance document from the USDA says that districts could also consider handing out multiple days’ worth of meals at a time.

“We do think that that would be the best strategy,” said Crystal FitzSimons, of the Food Research and Action Center. “It seems a little silly to be pulling people back into a site to get meals.”

Congress is considering proposals to remove certain regulations that make it harder for districts to continue to offer meals. Currently, districts can’t be reimbursed for offering meals in areas that are not low-income.

“I’ve heard that from a couple schools — we’re just going to get kids meals and we’ll worry about it later,” FitzSimons said.

Carissa Moffat Miller, the executive director of the Council of Chief State School Officers, said school districts need more flexibility and more money. “CCSSO urges Congress to approve new funding and flexibilities in existing programs, including but not limited to school nutrition, to allow states to operate these programs effectively under unprecedented circumstances,” she said in a statement.

🔗The economy

Closing schools would also have major consequences for the economy, which is already facing huge stress from the pandemic. One estimate suggests that closing all schools and daycares for four weeks would result in a $50 billion hit to the economy, or 0.2% of GDP. When kids are home, many parents miss work, too.

Some have argued that Congress should also expand access to food stamps, particularly for families with children — simultaneously addressing food insecurity and providing an economic boost. This is part of a bill that Congress is considering.

Another question is whether teachers and other staff will continue to be paid while school is out. Cutting off pay would of course harm staff, and could also hurt the economy more broadly.

“A lot of students and families are being thrust into situations they are not prepared for,” said Barbara McPherson, an educator in Washington’s Auburn School District. “Child care is a big issue as well as the unknown status of employment.” Seattle Public Schools, among the first districts to close down, said it will charge teachers three sick days, and then the district will cover up to 14 additional days. Some other districts have not made clear plans.

The full economic impact will depend on the federal government’s response.

🔗Summer school?

If students miss out on a significant amount of the school year, one solution is to expand summer school options.

Doug Harris, a Tulane University economist, has suggested the federal government fund such an effort. He proposed a roughly $8 billion stimulus to hire a third of American teachers to provide summer school over the course of six weeks.

Harris argues that this would also provide an economic boost, both by putting money in teachers’ pockets and allowing more parents to work by providing childcare during the summer.

“Yes, we can use modern technological tools to help students continue learning, at least a little, over the coming months,” Harris wrote. “But sometimes it’s best to fight the old-fashioned way. Summer school seems like one very promising approach to consider.”

Special education advocates have also suggested this would be a good way to make sure that students with disabilities are getting the services they missed while schools were closed.

🔗Testing

State tests are right around the corner, which means they’re likely to butt up against closures. And even if students return in time for tests, they will have lost instruction, raising questions about whether the exams could even provide a fair picture of student learning.

These exams have significant stakes — by federal law, they’re used to determine if schools are low-performing. Many districts also use them to decide whether students move on to the next grade, make admissions decisions for selective schools, and to evaluate teachers.

The U.S. Department of Education said Thursday that it would consider offering a one-year waiver for states and schools affected by closures. In turn, states might be able to get a waiver from the requirement of identifying low-performing schools for extra support. Other consequences would have to be figured out locally and at the state level.

The College Board also announced that it would cancel the administration of the SAT at hundreds of its testing centers.