Not all parents know their kids very well anymore this days...Most kids do their own stuffs and keep it secret... Kids who gamble and keeps it a secret looks like a smart kid to me, but not in a good way...Seriously, kids should always be told about bad effects of gambling and that they should not do it as it is not a good habit...  But if you are a parent and gambles also, then I think it will be hard for you to teach your kids not to do it...