As the door is opened by Miss Schlowski for Kimble to be introduced to the children, a crew member's hand is clearly seen holding the door open. The door also stays open despite obviously having a closing mechanism.
The ferret makes a high-pitched squeaking noise repeatedly. Though ferrets can make a wide range of noises, this is a noise that real ferrets do not make, though it is a common noise for "Hollywood ferrets" to do so.
Cullen Crisp Sr. returns back to the car, after he finally locates his Son at the school, and the Mother says for him to put out his cigar, because it's bad for children. Cullen is actually smoking a cigarette at the time he enters the automobile and the voice appeared to be dubbed into the scene.
When Kimble went to arrest Crisp he had his gun pointed at him but then the mall security guards tell Kimble to drop his gun, when the first ones came in Kimble looked at them with his gun still pointed at Crisp and because of him looking away Crisp would've easily disarmed him. This is not something a professional police officer would do.
On Kimble's second day of teaching, he is wearing a red shirt. When he picks up the little boy who is eating the lunches, he is wearing the outfit that he wore on the first day. After that, he is wearing the red shirt again.
After the class practices their Gettysburg Address recital in the gymnasium, Kimble is walking them back into the classroom as Zach is being rushed into school by his mother. She apologizes for him being late, claiming the car wouldn't start. But Zach could clearly be seen standing with his classmates during the practice recital earlier in the gym.
When Kimble tells all of the Kindergarteners to find a toy and bring it to the carpet, one boy gets his and sits on the carpet. In the next shot, we see him at the toy box getting a toy and sitting on the carpet again.
When Kimble introduces Phoebe, where she will talk about strangers, as he is talking the camera changes to the children. However in this shot you can see Kimble sitting on the piano bench, then it changes camera again to show him standing in front of them talking.
When Kimble goes into the street to confront Zach's father, there is a blue station wagon parked in the driveway of a home opposite the school, which an elderly man is washing with a garden hose. From the first close-up of Kimble grabbing the father, both the wagon and man are gone, and a dog is standing there instead.
When Pheobe is talking to John in the gym (while practicing the play for the fair) in one shot Pheobe has nothing in her hair, next shot she has a hair clip by her right ear, and next shot its gone again
On the first day at school, when Kimble asks for help with the bathroom issue, a little boy sits down to start on the lunch boxes when the little girl is in the hall holding herself. In the next shot, the boy is gone.
"John Kimble" is an odd name for an Austrian immigrant, which the character is and discusses at length. Kimble is a Scots or Welsh name, a variant of Campbell. It can be assumed that the name was Americanized upon immigration.
When Eleanor Crisp drives at Phoebe outside the school, the car stops right as it is about to hit O'Hara - this is very clear at the end of the shot, before cutting to a close-up of the impact. The vehicle's brake lights however have been disconnected to make it less obvious.