My first reaction upon reading this was that a student was being punished for kneeling in prayer on the stage ("Tebowing") but it appears that the boy might not have been truly praying at all but mocking the "Tebowing" gesture. If so, perhaps he deserves to be disciplined for his action.
When I graduated back in the dark ages, we rented our gowns and mortar boards. We were handed an empty folder on stage, and received our diplomas when we returned the caps and gowns.