A pile of exercise books was set on fire outside Cavendish School in Hemel Hempstead last night.
Firefighters were called at 11.45pm by a neighbour of the site who reported a loud mystery noise.
Crew commander Mark Mannell said: “He said he heard a bang – he said it was a really big bang, like the one at Buncefield.”
Four or five books of schoolwork that had been set alight were extinguished. It is not yet known whether the pupils’ work was current or not.