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
A memorial bench to remember Chloe Rutherford and Liam Curry will be unveiled outside South Shields Town Hall today.
The man in charge of policing the protests has said that all forms of non-violent protest will now no longer be tolerated.
A look ahead at the forecast for the Tyne Tees region.