The Haunting of Red-Rose High, I like the most.  

Ideas that come to my mind, would be that the teens would step into the school and they might have a few different pieces of equipment on them.  Like one teen would have their cell phone.  Another teen would have a compass, so as to not get lost in a strange abandoned school.  Another teen might happen to know sign language, which might help them communicate to a ghost if they encounter one, that is if ghosts exist in the story. 

Another idea is that there would be a role player playing the narrator for the story and the rest of the role players would each play a teen.  So basically the teens post that they enter the school, and the narrator posts what they encounter.  The teen players then post how they react to what they encounter and what they try to do, like trying to open a door the narrator wrote about being in front of them.  Then the narrator would post if they succeeded or not.  Basically the Teen players are trying to understand/live or survive in the Narrator's world of the Abandoned School.

My personal opinion is that the The Haunting of Red-Rose High, should have a puzzle element to it, that would present itself to the teens, that they have to solve or be lost/trapped forever/whatever other bad thing could happen to them.  :P