A Quebec private girls' school that held a hypnotism demonstration which left several students dazed says that in retrospect it should have taken the activity more seriously.

The demonstration by a young hypnotist at Quebec's College Sacre-Coeur on June 7, left one girl in a four-hour trance, five more students in a daze and 13 students feeling nauseous and with headaches. The hypnotists mentor had to be called in to snap the girls out of it, school officials said.

Principal Daniel Leveille said on Tuesday they didn't realise that people 14 and younger are more susceptible to hypnosis and they regret not seeking parental authorisation. - Sapa-AP