I agree with Wolfman about the withdrawing, but would offer a different opinion on the prior drinking issue. Although you may not technically have to put that on your application, and the school may never find out anyway, you might want to put it on your application anyway. Why you ask? Well, after law school, when you apply to sit for the Bar exam in your state, you will have to admit that charge regardless of whether it occured when you were a minor, and regardless of whether it has been expunged. The state bar will look at your law school application, and if they feel you were not forthcoming with the info, you may not pass the character and fitness test. Usually, you are better off by being honest in the beginning. There aren't many prior offenses that will keep you out of law school or from taking the bar exam, but being dishonest keeps people out every year!!! For example, in Ohio, there was a man admitted to the bar after being convicted of manslaughter several years ago. That same year, another man was not allowed to take the bar after he was not forthcoming about a misdemeanor charge!
Thus, I agree with wolfman in that you should call the school you are thinking of applying to. If they say you don't have to admit it, then document when you called, who you talked to, etc. This will help you three years from now when you have to apply for the bar.