I would advise against approaching the media if you aren't allowed to. The school may well make your life very difficult after this. On leaving school, we got written references.

Be polite and try to persuade the principal to allow you to wear a kilt. If he still won't allow you to, just wear a smart suit. Maybe not a tuxedo, since sooo many people seem to wear those.

I do agree that you should be allowed to wear a kilt.