The British Board of Film Classification.
Funded by the film industry the BBFC's job is to classify all films, DVD's, videos and even some video games.
There are a number of different classifications that a film could be and based on these our group has decided that our film should be rated a 15. This is because we will be targeting an audience of 15 and over as our genre is Teen Horror. A 15 allows us to be quite liberal when it comes to certain topics such as drugs and alcohol and it will also not hinder the violence planned to be in our film whilst still letting our film be shown to people younger than 18, meaning our film should get more profit as it has a bigger target audience.
To help us come to this conclusion we went on the official BBFC website to find the detailed classification for a 15 movie. http://www.bbfc.co.uk/classification/guidelines/15-2/