Character mistake: When Mikey looks at the Picture Day schedule, he points out that 4th grade is going last. However, the schedule says they are after 3rd grade and before 5th grade, actually making them fifth. The faculty is actually listed last on the schedule.
Continuity mistake: Near the end, Gus is standing between the two handball walls. He is looking back at TJ and Lawson, who are near the first wall. But as the camera pans out, TJ and Lawson have moved to the other handball wall.