You're first ammendment? What was ammended to you? A penis? YOUR PENIS GOT VIOLATED BY A SECURITY GUARD?!
Seriously though:
AFAIK, security guards carry no weapons (other than a MAG light, nice mace), so your in no harm physically if you walk to the office with him on your tail. Plus, they're not police, so they can't arrest you (I think it's assault if they attempt to handcuff you.. you could even call it sexual assault, because being handcuffed by another guy is really, really weird). Generally, when the situation comes up that I'd like to go to the office immediately, I follow this:
Joe: I need to go to the office. May I go?
Teacher: No.
Joe: Reguardless, I need to go to the office and you have no reason for denying me that privilege. Bye.