NYC has revived remote learning for a day. It was a mess.

New York City public schools on Tuesday began their first major experiment with remote learning since the coronavirus pandemic. During the winter storm, more than 900,000 students were asked to participate in virtual classes.

It didn't go well.

Many teachers, parents and students who tried to log in found themselves locked out of their classrooms. Instead of joining their video meetings, they received an error message: “The service you are trying to reach is temporarily unavailable.”

“It seems like a very broad problem,” said Jay Brown, an elected parent leader in southern Brooklyn who was trying to help his children log on while trying to work from home.

He added: “I know this is a huge undertaking. But the preparedness just seems to be lacking.”

On social media, dozens of people described a chaotic morning that brought back their worst memories of pandemic-era education.

“A total disaster,” Sam Green, who chose to take his 7-year-old son to McCarren Park to play in the snow, said in an interview. “I texted the teacher: 'Am I the only one having problems?' And no, the entire system crashed, even the director can't continue.”

Students dawdled during their first period with the cameras off, waiting for teachers who couldn't log in. Some were only able to continue after repeatedly refreshing their site. Others were kicked out of online meetings. As parents and educators took on the role of impromptu technical support, several schools canceled meetings and classes completely until at least 10 a.m., without even being able to attend.

One parent said his family had abandoned all remote learning for the day at 8:45 a.m., joining others who opted to declare a full snow day.

It was unclear Tuesday afternoon how widespread the technical problems were.

The Ministry of Education said on social media around 8:30 a.m. that it was “experiencing issues with services that require IBM authentication to log in.” Officials said an hour later that the company had “added capacity and improvements are being rolled out across the system.”

IBM did not immediately respond to a request for comment.

The disarray came after the school's chancellor, David C. Banks, said at a news conference Monday that while he expected some “problems,” he believed the city was ready for its return to remote learning.

“One of the good things that came out of the pandemic was our willingness to be ready for moments like these,” Banks said. “And I think the school system is more than prepared.”

Some students and teachers were able to log in without any problems. Alan Cohen, a parent in Central Queens, had his children, who are in kindergarten and third grade, set up their devices Monday night — and they successfully joined their virtual rooms.

Their classmates were not so lucky: “First there were three kids,” Mr. Cohen said, adding that parents' WhatsApp groups for the school and individual classes “exploded.”

“The idea that every child is going to be present for all their classes all day long has kind of gone out the window,” he said.

The city bought more than 550,000 kids' iPads and 175,000 Chromebook laptops during the pandemic, and the era of remote learning it ushered in has prompted many school districts across the country to forego traditional days off because of winter weather.

But Tuesday's debacle would certainly create a wave of resistance in New York. Shekar Krishnan, a city council member who represents parts of northern Queens, wrote on social media that the government “should have just given them the damn snow day!”

Some schools not run by the Ministry of Education did just that.

“It's just an old-fashioned snow day,” said Arthur Samuels, the founder of a high school in Brooklyn's Bushwick neighborhood.

“Too many students have to care for younger siblings, and we know how bad remote learning is,” Samuels said on social media. “We will see everyone again in person tomorrow. Enjoy the snow!”

Olivia Bensimon reporting contributed.