FREDERICTON -- A Maritime school board defended its decision to cancel classes hours before snow even started falling Monday, as critics questioned whether boards are too quick to call snow days that inconvenience parents and cost teaching time.

The Halifax Regional School Board was criticized on social media Monday as parents adjusted their schedules to accommodate children for a storm that still had not arrived well after the lunch hour.

"They have closed all schools due to a 'pending' storm. Not one flake of snow has dropped out of the sky," one woman wrote on Facebook.

But school board spokesman Doug Hadley said officials had information that the snow could start by 11 a.m.

"It wasn't the question of getting everyone to school, it was a question of getting everyone home safely," Hadley wrote in an email.

Paul Bennett, director of Schoolhouse Consulting, said closing schools is a rarity in many areas of the country. He said that as of 2010, schools in Winnipeg had not had a storm day since 1957 and Calgary had a policy that schools never close.

But he said schools in Atlantic Canada tend to close in anticipation of storms, noting that Monday's closure in Halifax -- the board's second snow day of the year -- impacted 137 schools, over 4,000 teachers and 40,000 students.

"We need long-term strategy based on the expectation of losing at least five days a year," said Bennett.

"We don't obsess so much with individual school days lost but we do concentrate all of our efforts finding policy solutions for chronic and repetitive school time loss. We do know that student performance and learning suffers after a succession of days lost," Bennett said.

He said in particular, math scores drop during years when the number of lost storm days is high.

There was a lot of public reaction last year when Nova Scotia's education minister suggested that students might have to go to classes on Saturdays as a way to make up lost time.

In New Brunswick, it was suggested that professional development days for teachers should be rescheduled after March to allow for more class time during the winter. Education Minister Serge Rousselle called for a contingency plan to be developed, but that's still in the works as the government develops a new 10-year education plan.

Bennett said schools need to consider sending work home when storms are expected, or using the Internet to deliver e-learning programs as is done in states like Vermont, Massachusetts and Ohio.

David Phillips, senior climatologist with Environment Canada, said Atlantic Canada tends to get more severe winter weather than the rest of the country, so it's no surprise the region gets more school storm days than other parts of Canada.

He said the Atlantic region leads the country for the number of snowfalls of 10 centimetres or more and the number of days of freezing rain.

"You get about 17 days (of freezing rain) in Prince Edward Island, while in Alberta you might get seven or British Columbia three on average. It's not a risk generally for school transportation the further you get away from Atlantic Canada," Phillips said.

Many parts of Atlantic Canada recorded record snowfalls last winter. Phillips said despite that, winters are getting milder and, in general, the amount of snow is declining.