A private girls' school in Quebec says a student was left in a four-hour trance and several others in a daze following a hypnotism demonstration.

Quebec's College Sacre-Coeur acknowledged Tuesday that it should have taken the June 7 activity more seriously.

Thirteen more students also complained of nausea and headaches, and the hypnotist's mentor had to be called in to snap the girls out of it, school officials said.

Principal Daniel Leveille said school officials did not realize that people 14 and younger are more susceptible to hypnosis, and said they regretted not seeking parental authorization.