Other mistake: When Don and his father are driving home and Don's father throws his ring out the window, Don gets out to search for the ring and you can see wet marks on his shins from kneeling on the wet road. However, he hasn't knelt down yet. It must have been from previous takes. Also, when he gets up after kneeling down, his jeans are dry.
Other mistake: In the game against Midland Lee there is a shot where the quarterback on Midland Lee is scrambling towards the sideline, if you look closely you can tell the quarterback is wearing a Riddell Revolution helmet. Riddell did not release this helmet till about the year 2000 and it is supposed to be 1988 in the movie.