Continuity mistake: In the scene where Jody is with her boyfriend on his bed, as he holds her neck the shot changes and he is holding her shoulder. This repeats a few times.
Other mistake: How did the murderer manage to remove the robe, put the wig on perfectly, and still be only a few seconds behind Jody and Kenny despite the fact that Jody and Kenny got at least a 5 minute start?
Continuity mistake: In the scene where the murderer is hacking down the front door with an axe, the door and its hinges change. In one shot the hinges are on the left (as we see it) and the door closes. The murderer then manages to hack through the door and the door swings open with hinges on both sides, opening like a swinging door from a western movie.
Continuity mistake: When Jody's dad (the sherrif) goes into the principal's office, you can see it's a small room with nothing to hide behind. He closes the door after him and seconds later the killer steps up behind him and knocks him unconcious. The killer couldn't have hidden in the room and the door opening would have been audible, so the killer appeared literally from thin air.
Continuity mistake: When Jody goes to hand some sort of project into her teacher, on the teacher's desk is a can of Cola, in different shots the can disappears and reappears.
Continuity mistake: When the Sheriff is called the the scene of the murder it is just gone 3am and pitch dark outside. In the next scene when he arrives in the woods it is broad daylight - The woods are just on the outskirts of town. How long did it take him to drive there?
Continuity mistake: When Jody is talking to Leonard Iveston, the word Byron is wiped out on the board behind them in the close up shots. When the camera goes to the long angle where most of the classroom can be seen, Byron is chalked onto the board.
Continuity mistake: In the dining hall, when Jody and her friend are having lunch, Jody's friend keeps looking at a boy. When the scene first shows you Jody and her friend, there is a can of Diet Cola in front of them, then in the next shot, its not Diet.
Continuity mistake: Did the whole storyline happen on one night? Three nights in a row there is a full moon, which is impossible.