An increasing number of teachers have their own websites, so sometimes starting virtual lessons is as simple as telling parents to check on snow days to see if any assignments are posted. Other times, the makeup work occurs afterward, with students completing assignments from home on days set aside for teacher training. Students can chat online with their teachers and ask questions via email.

In one school, younger students were directed to a website to play online money games, while older students in another school completed a simulation program to test how the angle of a baseball pitch affects the distance a ball is thrown.

The experiments appear to be the most prevalent in affluent private schools like Cameron’s, where only three of 643 students lacked a home computer.

At an all-girls boarding school in Simsbury, Conn., some teachers started using the Internet for lessons when roads become impassable so students who commute didn’t fall behind the others who live on campus.

“It’s been a really bad winter, so the teachers were grateful they could use these tools and not lose a day or cram too much material in one day,” said Vivian K. Elba, director of marketing and communications at Ethel Walker School.

But the efforts aren’t limited to wealthy, private schools. The Mississinawa Valley district on the Indiana-Ohio state line has led Ohio’s push for virtual snow days. Fifty-two percent of the district’s 700 students qualify for free or reduced-price lunches.

Since Mississinawa got permission last fall to make up two snow days electronically, four other Ohio districts joined the pilot program. Superintendent Lisa Wendel has received calls from other states interested in virtual make-up days.