Please, please, do not listen to the people in this thread encouraging taking the entire 2mg bar. When I was in high school my friend did this (and he had some experience with xanax), and he was in class passed out on his desk, I would try and wake him up and he would have a delayed response and sit up like 10 seconds after the matter, and get pissed off at me like a retard. So unless you want to get in trouble at school and probably black out, don't do it.
I have plenty of experience with xanax and other benzos, I never advocated or enjoyed "pushing limits" with benzos, what fun is blacking out? I understand the desire of doing drugs in school and not going to try and preach - but just do half of it (1mg), and you will have a great time at school and best of all, not black out and act like a dumbass.
If there's no way of talking you out of taking the whole thing, then don't do it at school. Take it at night so when you black out you will feel refreshed in the morning.
Oh and DO NOT drink alcohol with it unless you want to seriously endager your life.
Here's what I suggest: from your post history it appears you are prescribed Adderall, why not take Adderall for school, be productive, and after school when you start feeling the negatives of coming down off Adderall, take your decided dose of Xanax? Xanax is a known great substance for coming down off any stimulant. Be safe.