Continuity mistake: When Mr. Clark drives his car to the inner city school, he asks a punk where the faculty parking is. The punk points to the parking lot and as John drives away all of his tires are blown out by road spikes (he goes through a wrong way road). When he gets out of the car, notice that some of his tires have mysteriously reinflated themselves.
Continuity mistake: When Clark first meets principal Doyle he says "I don't think there is such thing as bad kids", while Victoria is hanging up a poster in the background. When it cuts to a close-up of Victoria she is looking in Clark's direction and the poster is up. It cuts again and Victoria is still hanging up the poster.