Bruno Santaguida, now 72 years old, pleaded guilty earlier this week to molestation and sexual assault.
Although police are only aware of one victim, who was under the age of 14 and who was abused between 1981 and 1983, investigators said they have reason to believe there are other victims unaccounted for.
Santaguida taught at Sir Wilfrid-Laurier Junior High School in Montreal North between 1975 and 1983, according to Montreal police.
The school has since closed.
He was arrested Oct. 9, 2012, after a complaint was filed against him in August 2011.
People who may have been victims of Santaguida are asked to go to their local police station.