"Now," frank stone says, pointing at the aerial plan overhead. "There are four ways to escape from a prisoner-of-war camp."
His audience sits up straight, waiting for him to continue. He nods briskly. "You can walk out through the gates in disguise. You can break through the wire. You can go over the wire. Or you can dig a hole under the wire." At this point, there is a shuffling among the ranks: this is why they are all here.
Mr Stone is one of the few surviving participants in the 1944 attempt to tunnel out of the German prisoner-of-war camp Stalag Luft III, fictionalised in the 1963 film The Great Escape, in which Steve McQueen took the third approach when motorcycling towards a barbed-wire fence near the Swiss border.
Now, at St Michael's primary, in the Derbyshire village of Hathersage, Mr Stone is telling the true story. And while there may be no motorbikes, it is no less stunt-heavy. He whips out a piece of pyjama cord, and explains how to construct a tunnel-lamp using only that, a lump of lard and an empty fish-paste tin.
Then he outlines how to make a compass out of a melted 78 record, a gramophone needle and a magnetised razor-blade. This is sealed with a piece of broken glass, submerged in water and shaped with kitchen scissors. "Break a window," Mr Stone begins, demonstrating his glass-cutting technique to craning children.
Eleven-year-old David Gibson's eyes widen. "How would you even come up with that crazy idea?" he says. "It's just amazing how ingenious the whole plan was, how they did this right under their captors' noses. They must have had a lot of courage just to attempt it."
"But you don't have to be big and important to do something like this," adds his classmate, Lizzie Colley. "They were just normal people."
Frank Stone enlisted as a gunner in the RAF at the age of 18. He had not yet started shaving when he was shot down by "Gerry". He was captured and taken to Stalag Luft III.
Much of what followed is now common knowledge. Camp inmates referred to the tunnels as "Tom", "Dick" and "Harry", and to dispose of displaced sand, diggers filled long-john legs and volunteers let it out marching around the compound.
"It's up to us to make sure the children hear the true story," says Catherine Nicklin, St Michael's history co-ordinator. "It's about questioning what you see on TV - that one person's view isn't always the truth. That's what history is about."
Of the 800 men involved in the tunnelling, 250 were chosen to escape. Only 90 made it through. All but three escapees were recaptured, and Hitler - "a very nasty man, I can assure you," Mr Stone says - had 50 shot. As a result, there were no further escapes from Stalag Luft III.
"Because they were so crammed together in the camp, they'd have made lots of friends," says Lizzie. "Some of his friends would have been killed. That must have been awful. Now he's living in a really nice village, but he'd never forget it."
David interrupts: "But he can pass it on to us. That's why he has to talk about it. And then we can pass it on to other people."
Frank Stone's account of the Great Escape will soon be available on DVD. Email firstname.lastname@example.org.