A Devon council is reviewing school trip security after three 10-year-old girls found a drunk man in their room during a visit to Belgium.
The girls were from Manadon Vale Primary School
The incident happened in June when the girls, from Manadon Vale Primary School in Plymouth, were woken in the middle of the night by the man's snoring.
The man apparently mistook their room for his own.
Plymouth City Council said it was now considering the implications of the incident for future school trips.
The man had no trouble getting into the girls' room at the Euro Hotel in Blankenberge, near Ostend, because they had been told by the school's authorities not to lock their doors in case they caused an obstacle in the event of a fire alarm.
But the move has raised major concerns, particularly after the recent conviction of a man for murdering a Cornish schoolgirl who broke into a room she was sharing with four classmates at a hostel in France.
Caroline Dickinson, 13, from Launceston, was murdered in July 1996 by Spaniard Francisco Arce Montes as she slept at a hostel in Pleine Fougeres, Britanny, France.
Montes, 54, was sentenced to 30 years in prison in June.
Councillor Dennis Camp, portfolio holder for schools and colleges on Plymouth City Council, admitted security against potentially dangerous intruders might be a greater priority than leaving doors open to allow swifter evacuation in the event of fire.
He said: "I think we we all learn things in retrospect, and this incident is something we shall learn from.
"As we now know there is always the possibility that something would go astray. It didn't to any malicious extent this time, I'm pleased to say.
"But there is always that risk and I'm sure the school will be looking at its procedures and the Local Education Authority will be looking at the guidance it gives to schools."
Parents of pupils on the trip said they had no criticisms of the school's safety procedures.
One mother, Nicky Flynn, whose son went on the trip, said: "There was a meeting with the parents before they went away.
"It was explained at that meeting that the doors were going to be left open at night and why the staff wanted that policy - and all the parents agreed to it."