Commercial gambling ads will be available only in the countries who supported gambling to grow and probably your government let this happen because they admitted gambling as industry and can be good source tax for them but besides all of it i think they will also thinking the risk behind it especially i read your post that there was casinos near to high school locations and it's very risky to childrens at there will attempts to gambling because casinos is too easy to be access
Governments should apply strict rules for those who wanna to gamble in such places. Casino industry is old,profitable industry due to gambling addiction based on human nature. This type of casinos mainly care about profit with minimum risk that's why guards are constantly rude against winners. Minimum gambling age is over 18 in my country,everyone should avoid to risk hard earned money there especially this age group. Sometimes i hear about teenagers who lost their tuition fee in casino. IMO casinos can ask the source of money with checking the detailed info of teenager participants in central system before entering with big money in order to minimize such cases.
I don't think that casino's would go to that detail though, why would they need to ask where the source of money came from? If they are within the age wherein they can enter a casino then they are mature enough to know the risk involved, just saying.
What the guards usually do, if they have doubts is to ask for ID to verify their age and that's it. If they show ID saying that they are 18 and above then they can play as long as they money in their pocket.
Also government doesn't allow casino's to be operated near schools or universities, so if student wanted to play then its their choice, imho.