Continuity mistake: When Terry Corrigan goes mad and teaches his students at gun point, he asks one of the thugs a question and holds his gun right up to his face. The tip of the gun is almost touching the thug's face, but from a different angle, the gun is further away.
Continuity mistake: When Jimmy is at the top of the flagpole, just before he falls off, every time the camera shows his face he is holding the flag straight out with his left arm. Anytime the camera is behind him, the flag is hanging down and both of his arms are wrapped around the flagpole. (00:33:13 - 00:34:00)