In the UK it means a type of (established, large, non-profit) what Americans call a private school. We call the latter in general independent schools.
In the rest of the world "public school" vs "private school" is pretty clear, I think you guys in UK are the only one to call private schools "public school" and public schools "state school".
In the rest of the world "public school" vs "private school" is pretty clear, I think you guys in UK are the only one to call private schools "public school" and public schools "state school".