Police allege the children, aged six, eight and 10 years old, started the fire in a classroom at South Broadview Elementary School Sunday afternoon.
Fire Chief Brad Shirley says it spread from some papers on a desk to the walls of the classroom.
The school's fire alarm alerted the fire department and when fire crews arrived they found smoke pouring out of a smashed window.
The fire did minimal damage, but Shirley says it could have easily spread.
"Certainly very concerning and unfortunately it does happen on occasion. The RCMP are investigating and we may also assist them by conducting some juvenile fire setting conversations with the young people, he said.
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