Yes,TTG, it's a weapon but, as stated, the law permits such a weapon to be with them in a public place,as Sikhs, 'for religious reasons' (and by Scotsmen in national costume), given the appropriate proof. The law also allows Sikhs on motorcycles not to wear helmets. If a Sikh wants to endanger himself, the argument must have run, then let him suffer the consequences.
I don't follow why anyone should be allowed to have a knife in a public place simply because their national dress includes a knife or a religion has sanctioned it. The defence is 'without prejudice to' the general one of 'good reason or lawful authority' (which is very difficult to establish). If someone is permitted to have a knife in a public place there must be both the temptation and the opportunity to use it unlawfully should the occasion arise (which is one reason why we have the law in the first place). The other specific defence, that the knife is for use at work, does make sense.It would be stupid to stop a carpenter or decorator having a knife for use at work when that, of necessity, means they have to have it in a public place on the way there !
This is a stunt. The boy can revert to being a ';man' once he's not in school. If he tried to enter many a building or board an aircraft with it he'd be stopped. What then would his father's argument be ?