Continuity mistake: Alex comes to work very hungover. He proceeds to spill coffee on his shirt twice. He then talks with Lisa in his classroom and now the shirt is clean.
Continuity mistake: Lisa invites Alex to dinner, while talking at the table we see a wide shot of the two of them with Alex's arm on his side. In the next shot his elbow is rested on the table.
Continuity mistake: In the sequence where Lisa Hammond undresses in the hallway, her underwear colour changes from black to white to black.
Continuity mistake: In the hallway scene following the locker search, Alex Jurel's hair mysterious transforms from neat to extremely messed up, in what is obviously an additional shot added later.
Character mistake: In the beginning of the movie everyone shows up on Monday. When Rosenberg is taking attendance he mispronounces the girl's name. She corrects him and he says yesterday and the day before it was something else. That would mean they came to school Sunday and Saturday.