Cadets with a well-developed curiosity and entirely proper lack of respect for petty-fogging rules can get over fences.
I don't think I would want a lump of corroded Harrier squashing the lad who is going to inherit my overdraft, if he were a cadet there. Or even just taking a lump out of his skull.
Not all H & S is nonsense. It takes maturity and bitter experience to recognise silly H&S from sensible H&S, and my money's on sensible in this one.