I spoke to th school when I saw the word, "brat" on their first words list (part of the reading system...), and felt embarrassed about doing so. I don't think it is a 'bad' word as such, just not suitable for out of context learning.
Anyway... my children say fart, I occassionally say it, try to say, 'fluff' but tbh they refer to the same thing.... And that doesn't need to be joked about... (but it obviously IS funny to lo's). Actually should be 'flatulence" shouldn't it?
Bum? Are you kidding.. in fact, isn't it a word some kids would say naturally instead of bottom? Better than arse, surely.
Sputum is a fab word, and way better that spit...
Poo is also a fab word that gets many chuckles... (rolls eyes)... it is also another word that crops up in the reading system (tho thankfully not as a one off word... "a poo at the zoo".
I often that all a slightly out there child comedian would need to do is say, "poo'... 'bottom', fluff fluff... farrrrt (with sound effects). Kids just roll around laughing... (again eyes roll).
Sorry tangent finished...
These words are pretty innocent, you won't be able to keep a straight face if you say these words to your DS's teacher, and TRUST me.... there are REALLY nasty words kids can come out with. The kid who is saying these things is not the one you need to worry about, he evidently has a grasp on 'humour', and is pretty smart... PLUS he is not really swearing.
Sorry... I have a 4 and 6 year old who regale each other with all these words.... I just look and say, "these words are not to be repeated elsewhere", while trying very hard to keep a straight face.