The school's Head of History, Susan Casey, says it is a remarkable find.
She is hoping money can be raised to conserve the shelter and turning it into a teaching facility.
More top news
Three people have been arrested today after an operation to clear a roadside protest camp.
Five men have appeared in court charged with the murder of a 27-year-old man.
The money raised by the North East Art Collective gallery's charity event in Newcastle will go to the West End Foodbank.