The school would definitely punish anyone engaging with gambling, drinking and smoking while using the uniform, in some cases, depending whether the school is a religious one, it could go as far as reaching to the professors and teachers themselves, so they have to make sure not to wear the uniform while doing those things. My bet is that the school never figured it out and nobody was willing sell out the identities of those teens to the authorities of the school anyways.
Again, if there is something I have learnt in this situations when people who is not supposed to be able to legally gamble manage to do it anyways, most of the times the clues point to the greed and the seek for profit which comes from the operator or owner of the betting place / casino.
Since all this is about money, then the solution would be easy, just by enforcing fines to those casinos/betting houses to allow children and teens to gamble would be enough for them to learn the lesson and ban children from entering the establishment completely.
I suspect that if the school found out that a student went to a casino shop, then of course he would get punished because it worsens the image of the school, let alone wearing a uniform unless he is not wearing a uniform then the parents themselves punish him.
Yes, it's like that, the school doesn't know about it outside of that, as for people who report to the school, most people don't care unless the person reporting it really wants to save him from gambling addiction, but still, if he is reported, he will get a severe punishment, maybe he will think again.
The authority to fine casinos is the government, how should the policy be carried out if there are rogue casinos that allow it, but this seems intentional if a child enters wearing a uniform and then gambles.
Still, the casino always warns that those under 18 years old should not play, but while this is easy to check in offline gambling, casinos that do not have a CIC before starting the game will not be able to do this. Moreover, players under 18 years of age can use tricks and go through the procedure of uploading parental documents. However, CICs have now become more reliable and require an online selfie of a person with a document, which will not allow you to go through this procedure.
Of course, it is better for young people not to play, they will have time to do this in the future, but I think that the danger lies in the fact that some of them have an irresistible desire to play, they are sure that they will win and will not have to do anything, including study. This undermines the foundations of development; the danger lies in such trifles.