I personally enjoyed this movie, and watched it when I was 13. --However, with parental supervision. I would rather that children of 12 years old at a SLEEPOVER NOT WATCH THIS. It speaks of unprotected sex, there is a sex scene, and of course, dirty dancing. Something that should not be seen by children barely even in middle school!
However, if you are a parent and want to let your kid see this rather touching story, by all means, do it. Just be careful and make sure they understand the errors in this movie.