The playground analogy here is like you gave your money to some kid, "Rusty" in the playground to buy a sandwich yesterday. Rusty buys a sandwich, and next day they come to pay you back. They in fact do pay you back by leaving some money on your desk. But then, before you've had a chance to put them in your pocket, some kid "Amanda" who fancies herself the class president (even though no-one voted for her), grabs the money from the desk and says "man, it sucks that Rusty didn't just pay you; what an ass, eh? We'll just put this in the 'class fund' for now". Meanwhile Rusty is like, hey I paid my debt the minute I put your money on your desk, so, sucks to be you I guess.
Yes, I get the part where Rusty was really mean to Ursula this morning, and that Amanda (who had been pretending to be Ursula's friend to get back at Rusty for a while now, and was what prompted Rusty's tantrum in the first place) made this edict about anyone giving Rusty sandwich money should not expect to get it back. And I get the part that it doesn't really matter if I gave the money yesterday, before all this started. Tough luck, I'm involved now.
I also get the part where I'd be reluctant to buy Rusty another sandwich if it meant Amanda would keep grabbing my money (though, in all honesty, I wouldn't trust my money with Amanda now either, given the whole "class fund" shenanigans), but ... seriously, that can't be the whole story, can it? Is the main story here really that we are all schoolchildren in dire need of a headmaster?