Shunning should be reserved for communities where people have chosen to come together with a shared belief system. It has no place in public organizations in a pluralistic society.
I'll second that. I'll also add that shunning is a practice designed to mark the shunned as an outcast with no standing in a group. This is very different from deciding you don't want to hang around with someone and leaving it at that. Shunning is a form of aggression and it's completely unacceptable in an environment like a school.
