The victims - six boys and one girl - were swept to their deaths in Glacier National Park in east-central British Columbia.
Ten other members of the group suffered injuries and were airlifted to hospital.
It was the second fatal avalanche in the area in the past 12 days.
Four Canadians and three Americans were killed in a similar incident while skiing down a remote glacier in the region last month.
Buried
The victims of the latest tragedy were part of a 17-strong group on an annual cross-country ski trip.
"
We are absolutely stricken with grief
"
Tony Macoun, headmaster
Two mountain guides who spotted the avalanche warned the students moments before it hit them.
A rescue operation was launched and seven helicopters were flown to the scene to airlift the victims out of the area.
Some of the skiers were buried in up to nine feet of snow (2.7 metres).
The dead pupils included six boys and one girl, all from Strathcona-Tweedsmuir School, near Calgary, Alberta.
"We are absolutely stricken with grief. Our hearts go out to all those who are impacted," said Tony Macoun, head of the school.
Two male teachers and a volunteer, who were leading the group, were all properly qualified, said Mr Macoun.
Park spokeswoman Pat Dunn said the group was equipped with shovels, beacons and probes.
She said the avalanche travelled for about a mile (1.6 kilometres) and had destroyed 10 acres (four hectares) of forest.
The area where the accident happened is not off limits and is popular with tourists.