My father used to say that sometimes, after a particularly bruising encounter with a class of CSE pupils. That was the gist, anyway, but I may have got any or all of the individual words wrong. But what a useful line it is! It tends to pop into my head unbidden whenever I see a group of juvenile delinquents - at least until I remind myself that they aren't actually doing anything more disgraceful than standing talking to each other, as is almost always the case.
Anyway, I assumed it was a quotation from the Old Testament - Proverbs, maybe, or one of the prophets - but doing a quick search just now I'm coming up empty. The nearest I can get is the bit in 2 Kings 18, when Rabshakeh is sent with his friends Rabsaris and Tartan (yes, Tartan!) by King Sennacharib to parley with the besieged inhabitants of Jerusalem, some of whom are indeed sitting on the city wall. He tells them, in effect, that if they don't cooperate they'll soon be reduced to eating dung and drinking piss.
Can that be what my father was quoting? Because, if so, he took the dung right out of context. Or maybe I've misremembered what he said, as the years have passed. Or maybe there's another text I've not found yet?