At 8:40 a.m., a mindfulness coach at a private preschool in Miami used Zoom to greet toddlers lounging on carpets, beds and couches at home. Their faces lit up when she sang and said she loved them.

At 8 a.m. in Nashville, Tennessee, charter school teachers met via Zoom while their principal beamed them onto Facebook Live. He reminded students to fill out the daily online survey about their well-being. "Do you feel safe at home?" is a question teachers monitor closely.

At 8:30 a.m. in a Milwaukee suburb, high school students logged on for their first practice day of remote learning. They wouldn't be expected to be online every day and working through new material until this week.

So went another week of school closures across America, where learning from home to limit the spread of the novel coronavirus has become an abnormal state of normal.

Even though nearly all American children have been home from school for almost a month, their experiences continue to be wildly divergent. Some districts pivoted immediately to online learning in mid-March. Others waited until this week to launch formal virtual learning plans. Some schools require work to be graded; others are telling teachers to give all students A's.

Some, but not all, of the differences boil down to family income and resources. It's hard to learn, especially remotely, if you don't have adequate shelter, steady meals, attentive parents, access to technology and familiarity with the English language.

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More than 12 million students in 2017 didn't have broadband internet in their homes, according to a federal report.

On top of that, there are additional worries: about the physical health of loved ones, unsteady personal finances, botched routines and the difficulty of working, studying and teaching in cramped environments.

The disruption and stress is likely to continue.More than 20 states, including Washington, Michigan and Pennsylvania, are now ordering or recommending school buildings shutter for the rest of the year, according to Education Week magazine. Mayor Bill de Blasio announced Saturday that New York City's public schools – the largest district in the nation – would also close through the academic term.

Still, Education Secretary Betsy DeVos said last week she expected learning to continue for all.

"We would hope that it’s an aspiration goal on the part of every single school district and school building to make sure that their students not only maintain their current level of knowledge and learning, but also expand," she said.

Many communities have already "figured this out," she added.

Private schools pivot nimbly to online learning

Many private schools, freed from bureaucratic red tape and bolstered by tuition fees, small classes and digitally savvy families, have pivoted gracefully. The Saklan School, in Moraga, California, used Zoom recently to hold virtual ukelele lessons with a music teacher and a flower dissection with a science teacher.

It took teachers a couple of days to learn 80% of what they needed to know to carry on with school in an online capacity, said Saklan's head of school, David O'Connell.

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At Centner Academy, the private school in Miami, the mindfulness coach who leads the morning Zoom class for preschoolers also hosts family counseling sessions and meditation for staff and parents.

Some public schools have had successes, too. The Miami-Dade County Public Schools has connected digitally with most of its students, a rarity among large urban public school systems. Many urban schools have struggled to bridge the digital divide with their lower-income families.

As of Thursday, about 91% of Miami-Dade's students had logged on remotely, said Superintendent Alberto Carvalho.

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Even before the pandemic, about 70% of students had a district-provided device or access to the internet, Carvalho said. The district had started revising a learning plan for school shutdowns at the end of December and early January, when it was clear the coronavirus was ravaging parts of Asia.

As Miami's school buildings closed, the district rushed to provide 90,000 more devices and around 11,000 Wi-Fi hotspots, Carvalho said.

Still, thousands of students will inevitably backslide. Not just in Miami, but everywhere. It's Carvalho's most pressing worry.

"We are bracing ourselves for an unprecedented, historic academic regression experienced by our most fragile population of students," he said.

Even some wealthier districts are struggling

Middle- and upper-income suburban districts have also struggled to help disadvantaged families get connected. Beyond that, expectations vary for student engagement and how much new material to cover.

Even within the same district, children's experiences can depend on who their teacher is.

"There's huge variance," said Elizabeth Self, an assistant professor of education at Vanderbilt University. "Sometimes districts are saying: 'This is the basic expectation.' But then among teachers in that district, there's a huge variance outside of that depending on their comfort with technology."

In suburban Milwaukee, two wealthy, adjacent districts took demonstrably different approaches.

Nicolet High School, a single-school district with about 1,000 students, raced to hold teacher meetings after March 13 and to create digital lesson plans. By March 17, the district expected students to log into the learning management system, Canvas, even as it worked to secure additional hot spots for students and staff.

Next door at the Whitefish Bay School District, which enrolls around 3,000 students, the district won't officially launch its virtual learning plan until this week, nearly a month after online learning started at Nicolet. Students logged on for two practice days last week. The delay prompted dozens of complaints by Whitefish Bay parents.

Some key differences: In Nicolet, the district is made up of only the high school, so leaders only had to worry about older students, most of whom already had district-issued laptops. Whitefish Bay students did not all have laptops, and the district had to figure out how to also serve younger learners. Whitefish Bay also chose not to have teachers gather in mid-March to work out the learning plans in person.

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Still, districts should not be judged on whether they were fast or slow to develop a plan, cautioned Maya Israel, an associate professor of educational technology at the University of Florida.

What's more important, she said, is whether the plan is developmentally appropriate, sensitive to the technological bandwidth people have in the homes, and responsive to the social and emotional needs of students and staff.

"The quick-rollout schools may have had to do more adjusting than the slow-rollout schools," she said.

Most schools are using paper packets

Despite so much conversation about online education, the most common model of remote learning has featured instructional packets prepared by teachers, according to Mathematica, a nonpartisan research organization.

With the long-term school closures looming, most districts are now moving toward offering more real-time support from teachers, through videoconferencing, phone calls or email.

Steven Malick and Felicia Hurwitz, two Mathematica researchers, have been combing previous studies for what works when it comes to remote learning.

"There is no research that really gets at our situation precisely," Malick said.

What's clear is that real-time engagement with teachers is necessary, they said. And students doing online courses on their own does not typically produce positive results.

So far, districts that have found a way to offer a full schedule of "live" classes are rare, Malick and Hurwitz said.

A small number of districts are using the crisis to completely reimagine what's possible, they said. For example, a school may decide to have a teacher who's really good at fractions teach all children the material, instead of just his or her own class.

Disadvantaged students will suffer the most

Most schools serving low-income students have faced daunting challenges in this new world of learning. And districts alone cannot always solve the problem of internet connectivity: Many families live in places where service is spotty or nonexistent.

As a result, many schools have no idea where some of their children are.

In Los Angeles, where about 80% of students live in poverty, 15,000 students are absent online and around 40,000 aren't checking in daily with teachers, according to The Los Angeles Times.

"You’re looking at fairly serious losses in learning time for kids," said Andy Rotherham, co-founder of Bellwether Education Partners, a nonprofit focused on improving schools. "The immediate challenge we need to triage is access."

Across California, only 59% of public-school parents surveyed in late March thought their district's learning plan was successful, according to a statewide poll. For those concerned their child would be unable to participate, 41% said not having enough computers or internet devices was the top barrier, according to poll results from The Education Trust-West, a group that advocates for educational justice.

"This isn't just an issue of devices," said Preston Smith, CEO of Rocketship Public Schools, a charter school organization that serves low-income students in three states and Washington, D.C.

"We're talking about trying to reach families that were already on the fringes of society, living in trauma and toxic stress," Smith said. "These parents are losing their jobs, or they're out there as low-wage workers, potentially being exposed."

Rocketship provided 2,500 Chromebooks and also Wi-Fi to families, but at least 20% to 40% of its students were still not connected, depending on the school, Smith said.

And after the first week of remote learning, online participation dropped off to around 50% to 70%, he added.

Still, staff have tried to uphold Rocketship's brand of joy and community online. Daily celebrations that open and close the school day are now simulated on Facebook Live. Teachers host lunchtime video conferences. Staff are connecting families with rent assistance or meals.

If students indicate on daily surveys that they haven't felt safe at home, staff follow up with them.

"We have a moral obligation to serve these students," Smith said. "We're figuring out how we push ourselves on innovation and equity and access."

Maybe it's OK to learn a little less right now

Despite the call from DeVos for students to learn new material, some education experts believe it's OK to reduce demands temporarily. Schools could pay less attention now to curriculum and grades and more attention to students' social and emotional needs.

"My fear is that everyone eventually hits a place where more and more people are sick, and this period stretches longer and longer, and the energy gets harder to sustain," said Self, at Vanderbilt. "What kids actually retain will inevitably suffer."

Schools should focus on laying plans for helping students catch up when buildings reopen, said Thomas Hatch, an education professor at Teachers College at Columbia University.

"We know that online learning doesn’t alleviate or ameliorate gaps in opportunities – it exacerbates them," Hatch said. "We have not designed our schools to enable students to get caught up, ever. This is an opportunity to rethink what’s really necessary."

Contact Erin Richards at (414) 207-3145 or erin.richards@usatoday.com. Follow her on Twitter at @emrichards.

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.