This is true cinematic brilliance, but not for kids or tweens. It may even be much too intense for some teenagers, but that's more of a case by case basis. It has VERY frightening and disturbing scenes/shots/themes/images. In fact, the movie as a whole is pretty disturbing. I'd show it to a mature high schooler, perhaps, who isn't easily shaken and has a tough stomach.
Easily one of the best films I have ever seen, and arguably the best horror film. It's just perfect, and is still scary and disturbing 40 years after its release.
Parents be warned: if this movie was released nowadays, it still would receive an R-rating. There is one disturbing rape sequence, and while the actual rape isn't really shown, you see nudity.