Children aged -15 years are never suitable for gambling because it can damage their behavior later in life.
It depends on their mindset. At the age of 15, I doubt they will have an interest on doing gambling.
But if they really did, more on it was because of their curiosity. I'm sure at that age they already know the difference between what's the good thing to do and not. If we try to force and convince them to ignore gambling the more they want to know about it.
Today's 15-year-olds are very smart, they know that in a casino the chances of winning are very low, they seek more fun than the same money, because most of them have no obligations, I know a neighbor who is 14 years old. And what he did was play warm and then from there he went to Axie Infinity, all the time every day I think he gets the 150SLP, every day, he also plays others like cryptoblade, plants, something like that and from all those games he always accumulates a lot of money And the most important thing is that he says that he does it because he likes it, that he knows he has money but he does it for fun, it should be noted that this child spends all day on a PC playing.
That's still illegal, as per their ToS. Anyone who is below 18 years old are not allowed to play the game, his axie team could be banned if someone will report it, so the better play on it is let his parent plays it. It is easy to play and anyone could understand it pretty quickly after watching some YouTube videos on how to play efficiently.
If he is a 18 year old kid, I would say that what he did was pretty impressive because not all of the kids thinks practically, the are more of a happy go lucky all the time.