Apart from billiards, there is also a chess tournament which is specifically for children aged 7 years and over, it is also supervised, whether those you see are supervised by their parents or run by themselves, but if we talk about the environment basically I haven't seen children go to the pool hall andplay there, unless there is a parent supervising him, because as far as I know, those who are adults are allowed to enter the billiard hall, perhaps other areas have billiard rules in other areas.
But if the kid goes alone to the pool hall and some people place bets there, it's clear that's not where he should be.