Students and staff from a Matlock school were forced to abandon their coach during a half-term trip to Paris after it was thought one or more people could be hiding under it.
Their suspicions were communicated to the French police, who seized the coach being used by the party from Highfields School, in Matlock.
Staff and students were provided with a substitute coach to allow them to return as planned last Tuesday night after their five-day trip to the French capital.
Co-head teacher Peter Cole said: “As part of the investigation by the French authorities, the coach the party was travelling on was taken for examination. Some students had left belongings on the coach, which have now been returned.
“A substitute coach was provided, ensuring that there was no disruption to the itinerary and the party arrived home safely on Tuesday night as planned.”
Mr Cole said that the students and staff were not in any danger at any point.
He added: “Our students behaved in an exemplary fashion throughout. They were superbly supported by an experienced group of staff, who ensured that they had a very productive and enjoyable visit.
“We remain committed to providing students with the excellent opportunities that foreign trips provide and will take into account all relevant factors in future planning.”
One parent, who did not wish to be named, said he understood that illegal immigrants had been stowing away in the luggage compartment of the coach.
He said: “It is concerning that no-one knew they were there and that our young people had to abandon some of their belongings while all of this was going on. Maybe schools need to think twice about going through Calais with youngsters, while the current problems associated with the camp there is sorted out.”
Another parent, who also preferred not to be named, added: “I am pleased that our children behaved well during this event but feel it should not have happened in the first place.”
A number of similar incidents have taken place over the last couple of years, with illegal immigrants stowing away on schools coaches. In at least a couple of incidents, the stowaways made it into the UK and surprised everyone when they climbed out of luggage compartments in London and Birmingham.
Earlier this year, a school coach, returning to the Isle of Skye, was attacked by what was said at the time to be “stone-throwing Calais migrants”.