If the rules say you have no alternative but to do something you know is unjust, that is when you refuse to obey them, and they can sack you if they want to.

If soldiers in a life and death situation are bound in honour and duty to refuse to obey orders to commit war crimes, that has to apply to school superintendents in a matter like this.

But in any case, as has being pointed out, this was not a knife which had been "designed to cut or stab another by being thrown", so he didn't even need to defy the rules.

Though is that rule misquoted in that report, with an "or" being missed out? It seems to say it's alright to have a knife so long as it isn't designed to be thrown. Crocodile Dundee with his machete would have been fine, it appears.