I don't want to turn this into a cop-bashing thread. I have had encounters with several cops and all of them have been polite and professional. Of couse, none of them thought that I was a suspect. If a cop suspects that you did something, they are going to try their hardest to get you to give something away. That is their job and can be quite handy when dealing with criminal, however, it can be quite uncomfortable if you are innocent and the cop doesn't believe you.
Now if one of your school administrators tells the cop "This kid is trouble, He's the type who would do this, etc" then the cop is allready suspicious. When they question you, stay calm and tell them where you were and what you know. If they don't believe you and try to lean on you/threaten you ask to call your parents and then stop talking.
By yourself you are in a weak position, get frustrated, lash out, act smart, and they can make things a lot worse for you. If they don't believe that you weren't involved get your parents or a lawyer there before you say anything else. You are less likely to be bullied if you have an adult on your side.
Not all cops and school admins are out to get non-conformist kids, but every once in a while you run into the type who are either out to get you, over zealous, or just plain ignorant. As a minor in high school you are in a losing position and you have to choose your battles carfully. There is no point in standing up to "the Man" in this situation where you have nothing to gain and lots to lose.
I hope things turn out allright for you,
TheFabulousFink