Corrected entry: This movie was filmed at my school, so perhaps me and others from GSGIS will be the only that will understand this but when the characters leave a 2nd floor class room (our chorus room: I believe an English class in the movie) they come out and miraculously are on the 1st floor.
Corrected entry: When Jody and the other girl are in the police station after her first attack, Jody's friend tells her that Cindy is holding a meeting at lunch. But the clock behind her say 2:30 which would be near the end of the last period.
Correction: The clock is wrong. It happens.
Correction: It may be your school in real life, but this is a movie. There is no suggestion of what floor is what in the movie, nor any suggestion of which floor the classroom is on so this is not a mistake.