For saying something negative you have too watch everything. Saying this, it is a totally bad acting teenage movie. They could make a turnover saying that the killer was Amy for some kind of mental disorder and saying that the teacher was a representation of her and the trauma of her father's death which was killed by herself in a act of becoming a serial killer. I would have done that to make it a couple of stars up and to make it quite decent. Even the murder of Amy's mother boyfriend could be explain by her desire of keeping away all the potential men trying to come close to her mother. I hope this is what you wanted as well.
Review of Girl at the Window
