Limiting screen time and telling students to hush are things of the past now that coronavirus has many teachers swapping whiteboards for laptops.

Ten days after transitioning online, French and Spanish teacher Constance Du Bois says the current situation has "nothing to do with classroom teaching."

The 37-year-old Franco-American teaches at New York's United Nations International School, a private institution of 1,600 students that is far better equipped than the city's public schools.

But even in a school that already uses many tools of online communication -- and serves privileged families with easy internet access -- Du Bois says transitioning to online teaching did not come without challenges.

Instructors there had already begun planning to teach online in early April after spring break -- but those plans sped up once a professor was diagnosed with COVID-19, which has now infected nearly 5,000 people in the United States' largest city.

The school closed immediately after learning of the positive test -- before the online curriculum was ready.

The first difficulties were technical, Du Bois told AFP via video conference.

"We tested the program with a few students, but in reality, we weren't yet acquainted with the platform," she said, having just finished a lesson with teenagers aged 14-15 in front of her computer at home in Brooklyn.

"The students had plenty of technical problems, lots of crashes."

Even once those basics were resolved, other, more structural problems appeared.

- Isolated students -

At first the platform -- called "BigBlueButton" -- did not allow the students to see each other, only the teacher.

"There was no ambiance in the class," Du Bois said. "They're really missing the social side."

"They want to go back to school, they're sick of not seeing each other... they feel very isolated."

It also takes longer to prepare the lessons, and the struggling students are harder to spot.

In a bid to overcome these difficulties, she is splitting them into small groups -- the platform allows her to break up the class into "small virtual rooms."

The method allows two to three kids to see each other and talk among themselves, she said.

The school also had initially modeled its online timeline on the normal schedule -- but teachers quickly realized "the students were spending their entire day in front of the screen, and us too," Du Bois said.

The school therefore shortened each class from one hour to 40 minutes.

"It's a relief for us, and the students are suddenly more focused," said Du Bois.

Like thousands of teachers worldwide, she has no idea how long her school will remain closed.

She does know already she will teach online at least until April 20, when New York schools expect for now to re-open.

Some US cities, however, have already announced they will stay shut through the end of the school year.

"There are a lot of teachers who are quite anxious over the idea of not being able to finish the curriculum," Du Bois said. "We will have to be more flexible at the beginning of next school year about what students should have achieved by the end of this one."

It's not all bad, though, as teachers learn to "adapt their methods" to manage online courses.

And she said students are doing their part: "The students are very conscientious, connect on time, do their work and participate."