Tougher yet is the technology. Most schools don't have one-to-one programs that supply students and staff with computers, and home Internet connections can still be spotty. Teachers polled for a 2013 survey by Pew Research Center's Internet & American Life Project said more than half of students had sufficient access to digital tools at school, but only a fifth could access digital tools at home.
Even without schoolwide technology programs, individuals teachers are finding ways to keep their students on track.
The day before a February snowstorm swept through the Atlanta area, teacher Jordan Kohanim sent her students home with the same instructions she repeated all year: Check the class website.
Most of her students at Northview High School outside Atlanta have made it a habit, and with the help of tools such as Remind101, a service that allows teachers to send text messages to students, she was confident they would follow through. When an earlier stretch of bad weather caught schools by surprise, several students checked the website and completed assignments without her asking, she said.
It's not the highest quality education out there, Kohanim said -- there's little chance for interaction when students are asked to read a passage, watch a video and write a response. But Kohanim made herself available to answer questions and check work, and it helped to keep students focused until they returned the following week.
"I wouldn't say I'd like that to go on for long," said Kohanim, who has maintained a class website since she started teaching seven years ago. "We don't have time to stop on snow days. We have to keep moving."
'A nerd's dream'
On the morning of Feb. 13, Pascack Valley High School English teacher Matt Morone was maybe a quarter of the way through his morning coffee when students began to respond to "The Autobiography of Malcolm X" on Twitter. Some teachers used Google documents or learning tools such as My Big Campus, Schoology or Canvas for the virtual school day, but he especially liked seeing the conversation draw people who weren't even in his class.
"This was a nerd's dream for me," said Morone, himself a graduate of Pascack Valley Regional schools.
For students, it was a lesson in time management and self-driven learning, one he's sure they'll take to college. For teachers, it was a chance to try ideas they've only pondered before. For everyone else? Proof.
"We are in a fortunate position here ... but you don't need a whole lot of infrastructure to do some of the stuff we're doing," Morone said. "There are means by which to do this. A lot of Twitter discussion is through iPads, cellphones -- whichever glowing rectangle you want to use, that's fine."
Students were learning other lessons, too.
Zak Terzini discovered he had to be concise because he only had 140 characters to make his point about "Malcolm X." He listened more, too. He's "a talker," he said -- an athlete, the class president, a guy who's always ready to jump in with an opinion.
Online, he finally heard some quieter classmates speak up.
"Having it all out on Twitter, people have that little barrier," he said. "It was kind of open to a lot more opinions."
Between shoveling snow, watching an Olympic hockey game and making himself a sandwich, he listened to a teacher explain some algebra concepts, completed some history work and forced himself to figure out some stoichiometry problems that he might've given up on if he'd been in the same room as the chemistry teacher.
"I thought, 'We're just going to get extra homework.' It was kind of ridiculous to have a virtual day," he said. "But the mood definitely changed after it went successfully. They got us involved. They were assigning the right amount of work.
"I got done at 2:51, and I can't believe I actually got done."