Teenage binge drinking is apparently quite the trend. I would do some research on this with your son and other children so that you can research this together and learn about it together. It is not uncommon, but can be dangerous.
I say bring this issue out in the open and get your kids involved in it. It is information that they should have and need to have. Getting angry is pointless. Knowledge is power and gives them more choices and tools. Just my honest opinion.
Having an alcoholic for a parent or being raised in this environment does up someone's chances of being one themselves.