Other mistake: When the boys cause a mini tremor by blowing up the girls' base, the time at which it occurs is strange because when they do it, both Stan's parents are at home (even though they both have jobs), Ms. Choksondik and Mr. Mackey are at Choksondik's house getting it on (indicating that school is over) and the other teachers are still at the school.
Continuity mistake: When Miss Chokesondik first lectures the girls on STD's the words "Sexually Transmitted Diseases" appear on the blackboard although partially obscured as it is a narrow shot of the teacher. The view then changes to a wide shot of the blackboard and nothing is written on it. Miss Chokesondik then proceeds to write "Sexually Transmitted Diseases" on the board. (00:05:35)