I wouldn't contact them without talking to the principal first. If I were the principal I would be extremely upset if somebody reported it. It should come from her and you should give her the chance to be the first to do so. You have your child in the school and you don't want any unnecessary problems with the principal.
I would go and talk to the principal again and ask her what the current situation is. To this day I remember when my father complained about my teacher to the principal and of course, the one who ended up in trouble was me. Just my two cents.
