Well, when I was in high school it was usually used as a social gathering beverage, or they thought of it as a competition to who could hold their alcohol best. For me personally, I could never get over how relaxed I was when I drank. There are many reasons why we have so many underaged drinkers but majority is to feel grown up. If you have a problem with an underaged drinker and you want them to stop, I would pin point the reason why they were drinking and go from there. If they are drinking because they think they are grown up, warn them of what they are doing wrong and what could happen, and if they don't listen, don't worry, they will learn soon enough. If they are drinking to feel grown up, then let them do grown up stuff that is legal for their age. Tell them gently it is not mature to drink underage, but don't yell at them like they are a kid, it will only send them backwards. You can give them that grown up feeling, not alcohol.