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.
The newspaper Roger shows Alex with the pictures Eddie took is smooth when seen from one angle but crumpled when seen from the opposite angle.
As Alex and Eddie discuss the stolen car and Eddie returning to take a remedial reading class, Alex's coat and hair change from zipped and combed, to unzipped and messy in one series of dialog, then back to zipped and combed at the end of the scene.
When Lisa and Alex are having dinner, Lisa's wine glass goes from full to half full and back again.
In the opening credits it's snowing, stops and snows again. Lisa is seen walking toward the school in the snow and when she's at the front door its stopped snowing.
The "red wine" at dinner is very clearly not wine. To be that bright, thin, and translucent, it was most likely juice. (This was most likely because of Nick Nolte's intense struggles with alcoholism at the time.)
In the scene when JoBeth Williams strips, when she has her back turned you can see the top of white panties. When she turns and runs down the hall, the pantie are black.
Rubell would be expected to know Ditto's real name, especially since he had been teaching there for many years.
When Eddie presents his slide show to the class, in the last slide Alex is shown smoking a cigarette. Schools generally prohibit smoking inside of its buildings and most definitely inside of classrooms.
It is highly unlikely that a college educated teacher wouldn't know how to spell a five letter industry standard word like "tardy".
When questioning one of the students on how her name is pronounced, Rosenbloom refers to the fact that just yesterday, she said it was something different. It had already been established that this scene was taking place on a Monday, which would have made Sunday the previous day. Highly doubtful that school was in session on a Sunday.