A head teacher said he was forced into his school's kitchen due to ongoing problems with a hot meal service provided by a private company.
Malmesbury School's head teacher Brett Jouny said G4S had been unable to supply "the right number" of catering staff for weeks and the issues had threatened the school's Christmas dinner, which ultimately went ahead.
He said in addition to his normal duties, he had been serving burgers in the school cafeteria "because the number of staff available has been so poor".
G4S refuted the claims and said it had "delivered a full lunch service" with the exception of one day in early-December.