I Just Forgot question

Ok so I can't remember the title of this novel but I read it about 5-6 years ago (so lets say 2010ish) in high school and can't remember the name of it!! It was about a bunch of kids who were locked up in a kind of psychiatric ward due to things that were wrong with them such as extremely think skin (cant remember what was wrong with the other kids). They were kept there to 'keep them safe' since it was 'too dangerous outside'. There was the main lady who would give them their pills and take their blood etc. Then one day four of these kids escape. I can't really remember what happens but in the end I remember that they all die ('reach the light'). Also I don't think the kids know that they are in a psychiatric ward, they've grown up there and don't actually know where they are. Any help would be greatly appreciated!!! I need to remember this title for my English assignment!!!!!! Also sorry if its a bit vague, I can't remember anything else about it!!