Age ratings are something that shows at the start of almost every trailer imaginable (because most trailers are produced from America, the ratings use their system). The picture below details the classic green-screen that you get at the start, usually accompanied with the rating of either G or PG (General audience, or Parental Guidance). Trailers are rarely produced where they would be rated higher, because it is hard to restrict the audience that may see the trailer, ergo, production companies try to produce trailers that are suitable for all.
After looking at my storyboard, I have decided to rate my trailer a 'PG', as there is no real use of violence, guns or drugs, nor is their anything to insinuate that you go out and stab someone. The film however is designed to be scary, and there are perhaps a couple of 'sensitive' scary moments in the trailer, so parental guidance will be advised.
