Since the age was not included I can simply say, yes. Kids ages 12 to whatever can watch horror movies : ] They should be able to at that age because during that time they're also exposed to a lot of other things that are important in a child's life. Horror movies are just another thing that everyone's doing, and if you don't like horror movies, that's your decision. If it affects you in a bad way, maybe you shouldn't watch them. But other than that it's completely fine.
Kids should not watch horror movies because it won't make them feel better about their fears but it will encourage their fears and add to it
and most kids may not know or forget that this all is acting because modern day horror movies use realistic CGI effects so the kids will have psychological problems and will be afraid of everything *AND I MEAN EVERYTHING*
When I was little I had nightmares for weeks after watching CORALINE. An actual horror movie would of been horrible, just don't show a kid a horror movie. Seriously, by the time they are eight or so the most even then they should watch is beetlejuice, Honestly I don't understand watching horror movies at other ages either.
The kids would be horrifies with the horror movies, and they might not be able to concentrate, because you just saw a zombie wondering around in the TV. They should be protected their eyes. There are a lots of movies that kids can enjoy while there in 5-10 years old.