Things about this movie I don't get

-The Miss Devine character made no sense to me. She's a sub that knows nothing about this boy, yet she's all in the business. And why even write her into the story as a sub. She'd make more sense if she was the actual teacher who knew the kid well.

-Was the mom going to actual stab her son? For what. There's a few things in that scene that made me feel she wasn't, yet there they were. I feel as if that was a senselessly contrived scene just to stir up some action/horror.

-It becomes clear Sarah is more than just a girl in the wall. But it's unclear what she is exactly, how it happened, and why they decided to put in the wall. Supernatural? Telekinetic? Super strong? How the hell was she unable to escape from the house. Why did she kill the teen crew so quickly, but was different towards Miss Devine.

IMO, this movie could've been the best horror movie of the year. The story was suspenseful and interesting. The cinematography was top-notch. It looked and felt creepy. But it fell off the rails once she came out of that wall, and that didn't need to happen. The ending was lazy and all it would've taken as a few sentences or a few scenes to clear things up. Epic fail.