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
Vera Robinson MBE has died at the age of 101. She had been a fundraiser for the Redcar RNLI lifeboat station since she was 16 years old.
Provisional statistics for July show it was a cool and wet month for many of us.
With just 49 days until the start of the Rugby World Cup, the Webb Ellis Cup is touring our region.