I know that most schools have rules that limit off-campus interaction between teachers and students, but what if we just took the gloves off?
In other words, let the teachers/principals/whoever fight back online. Example scenario:
Jimmy (student) on Facebook says: Mr Pasquerella is fugly as hell, and he has really bad BO.
Mr. Pasquerella (teacher) on FB: Well, that's really cute Jimmy, but the fact is that your Momma never complains about my dashing looks OR my BO. She did, however, tell me that she wishes she aborted her waste-of-flesh kid--who couldn't get a D in social studies if his life depended on it--when she had the chance.