Bring it to the eye of your school board. Student privacy should be in the handbook, so it'd have to be anonymous, for safety purposes. Also, this should more be brought to the attention of your school counselor, since this is one of the issues they deal with and know how to handle. Anyone can go on anonymously and say someone bullied them, just to get the other person in trouble. You must talk about it in person. Having it online may not have the best outcome.