Show-and-tell at a British school could have ended very differently after a student unknowingly took a live explosive device to show off to his classmates – which had to be detonated by a military bomb squad.

The unidentified student – excited to showcase his grandfather’s World War II-era memorabilia – brought in the vintage shell along with medals for show-and-tell last month to a class full of nine and 10-year-olds at Kingsacre Primary School in Devon, about 200 miles west of London.

“(The items) had been kept in the family home for decades,” the school’s head teacher Claire Cole told Devon Live. “They were displayed to the class but at no time were they handed. The next day the artifacts were collected by the grandfather.”

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The child’s family originally believed the shell was inert; however, the child’s grandfather realized the device might still be active.

A concerned parent said that the grandfather collected it from the school, “put it in the boot of his car and drove it to the Barnstable police station.”

“He went into the police station and explained what he had in the back of his car,” the parent added. “His car was surrounded and the military were called.”

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Officials told Devon Live that the military took the device to another location, where it was buried and detonated as a precaution.

"We have to be careful about what is lurking in our cupboards,” Peter Wooldridge, media communications officer for the Royal Navy, told Devon Live. “The family, in this case, did the right thing by passing it over to the police, but really these devices are best left untouched.”

The concerned parent said school officials had yet to inform all parents of the “massive breach in health and safety and the safeguarding of our children.”

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Cole said the school “clearly needs to review our procedures for show-and-tell.”