research about pg-13 movies

I did research on if should 4th graders watch pg-13 movies. What I found out what that if young kids should watch pg-13 usually when they watch scary pg- 13 movies they get nightmares. When they watch inappropriate movies they think its okay to say things inappropriate stuff or bad words. And when they see pg-13 movies about violence they will most likely like to fight and become violent. So young kids (under the age of thirteen) shouldn't watch pg-13 movies!!!