That makes no sense at all. What on earth does the pupil have to do to be classified as 'a genuine emergency'? Burst into tears and plead for clemency? ???
Try and impose the adult equivalent on, say, the North Stand for the first 30 minutes of a game.
When you gotta go, you gotta go.
About as sensible a rule as the one the head of the school in Patcham this past week tried to impose on the wearing of coats other than thirty quid school-branded coats to school. In temperatures close to zero. Non-school-branded coats were confiscated and had to be collected by the parents...