It's not a private school, btw (know ds1's is, Pag). I get the impression it's the general culture, I don't know any parents yet! One mother did phone me when her ds was coming here to be reassured that they would be supervised and there wouldn't be alcohol - I was surprised at the time, I'm not now .
It's that odd kind of middle England, home county, commuters, heavy drinking, private-prepped, tutored, rugby and tennis club membership thing where the parents seem to think it's ok for the kids to have a drink. I have never come across this, but dh grew up in that kind of land.
I don't know if I can say to ds that if he isn't able to say nah, don't drink thanks, that he can't go.
And I was so pleased when he got in