Continuity mistake: When the Officer David Delinko and The Captain are having some lunch in the seafood restaurant, the cups on the table move about between shots during the scene.
Continuity mistake: Firstly we see that the number on Officer David Delinko's police car is eighteen. However later it has suddenly changed to twenty-four.
Continuity mistake: When the burlap bag is placed on top of Roy's head, the bag has suddenly changed position after they come through the trees afterwards.
Continuity mistake: When Officer Delinko is chasing Roy in his police cruiser, he backs it into a tree and the bumper of his car get damaged. In the next shot there is no damage done to the back.
Continuity mistake: In the room where Officer Delinko is interrogating Matherson, the sunlight coming through the window shines directly on walls that are opposite each other (i.e. it shines on both the north and south walls).
Continuity mistake: When Officer Delinko cuffs Dana Matherson, who has mouse traps hanging off his clothes, the amount of dirt on Matherson's shirt repeatedly changes, depending on the angle of the shot.
Continuity mistake: When Roy tapes up the gauze on Mullet Fingers' dog bite, the length and position of the tape strips change (and gauze as well) in the following shots, including their trek on the boat.
Answer: A straightforward answer is because these events happened in the context of a movie and the writer simply did not have the bus driver respond or Dana get in trouble. Only the writer could tell you why. If these events happened in the real world, there are several possible answers. The bus driver's job description may not have a provision to discipline students. Her primary duty is driving the bus in a safe manner to get the kids home safely. A driver must watch the road and traffic, not passengers. Her quick glance in the rear view mirror would not enable her to see all that transpired. To take action would involve stopping the bus and getting off schedule; the kids would get home late and their parents would be worried waiting for the bus. Maybe she just didn't want to get involved. She could get injured if she tried to intervene. Bus drivers might get fired if they hurt a student even when breaking up a fight. She may have thought the kids need to stand up for themselves.
KeyZOid
Why didn't the bully get in trouble? Maybe because the adults/ school officials thought the broken nose was enough punishment for his behavior. Maybe the bully is a persistent problem and trying to discipline him would only make matters worse. Maybe his parents are just as bad or worse and the school didn't want to deal with them. Maybe no-one reported that the bully started it and was choking Roy because they were afraid of him and didn't want him to retaliate. The bully looked like the victim, not offender. Maybe others thought the bully's home situation was awful and he already had a difficult life and a lot of stress. Maybe the bully has a psychiatric disorder and/or takes medication that increases his aggression. Maybe the adults also think the kids need to work out their differences amongst themselves. Maybe the bully is already under the supervision of the juvenile probation office and - one more offense - would be certified to the adult court and get even worse.