Deliberate mistake: When Melanie first walks into the classroom she sees five rows of students. Later when the students are about to leave there are only four rows of students, now ending with the boy in the plaid shirt (closest to the camera), in the front. The row on the left has been removed so the camera can pan from left to right in the side shot. (01:08:50 - 01:13:00)????
Continuity mistake: There are two different perspectives when Mitch puts the peroxide on Melanie's cut. The first is the close-up of her face and there's no blood on the piece of cotton. The second is the close-up of him and in these shots there's plenty of blood on the cotton, and they keep switching between the shots. (00:27:35)????