i had the same thing happen to me when i was 15.
I explained the security flaw, but they didn't understand a word i was saying. I ended up being suspended for three days and they deleted my login.
Naturaly being 15 i wasn't to happy and used an apple computer to create an admin account.
i spent the rest of my last year at the jr high (freshman are at the jr high at the school i went to) making the IT guy's (just some old guy who didn't know much about modern security) life a living hell.