Don't take something that causes retrograde amnesia at 2mg (at your tolerance) before you need to learn things, that's such a stupid plan... just take it after school or on a Friday. If this is for medicinal use, you're so anxious that you can't even leave your home to go to class, then take one quarter (0.5mg), and cut that in half. Even 0.25mg Xanax will impair you cognitively without a tolerance, so I recommend that you leave it in your pocket and only use it as needed (when you feel a panic attack coming on) at school, or take 0.25mg as need in the morning if you are suffering from agoraphobia.
If it's for recreational use, follow tricomb's advice.
You have a benzo that is meant strictly to abort panic attacks, so it's meant to knock your ass out quickly, and leave your system quickly as well. A much more suitable benzo for having a mellow day without being fucked up is diazepam, at a dosage of 5mg, or clonazepam, at a dosage of 0.25mg (equivalent to 5mg diazepam). These are assuming that you don't have a benzo tolerance, as you say that "you don't know much about [them]."