Wow, I like that movie and actually own it, but I'm surprised to hear they showed it at a school. Usually the schools err on the side of overly cautious. I remember at one school gathering for Valentine's Day they showed us Cinderella, and we were in high school!
While I'm sure most of the kids there have seen worse (or at least as bad), and it won't scar them for life, it was out of line on the school's part.