Mullet Fingers: You've got to start thinking like an outlaw.
Curly Branitt: What do we do about them owls?
Chuck Muckle: What owls?
Curly Branitt: Well, the ones we got... you know, in the little.
Chuck Muckle: This time at half-speed, Branitt: ignore owls, or lose job.
Chuck Muckle: Mr. Branitt, what does one hundred pancake houses sound like to you?
Curly Branitt: It sounds like an awful lot of pancake houses.
Chuck Muckle: It will be a record! I will be the first regional manager in the history of Mother Paula's to reach one hundred pancake houses. And that is the stuff that food and beverage industry legends are made of! Ah... it is my dream. And you are responsible, Mr. Branitt, for making a tiny piece of that very big dream come true.
Roy Eberhardt: What's wrong with Ling Ho?
Roy Eberhardt: Hey, Dad?
Mr. Eberhardt: Yeah?
Roy Eberhardt: What do you do to catch the bad guys?
Mr. Eberhardt: At work? Well, we don't chase our bad guys down the street. The trick is to catch them in their paperwork. Sooner or later, they all slip up and leave a trail.
Roy Eberhardt: Right.
Mr. Eberhardt: I know it's boring stuff, it's not the razzle-dazzle you were hoping for.
Roy Eberhardt: I don't know. Maybe it is.
Roy Eberhardt: I knew I couldn't spend the rest of the school year hiding from Beatrice the Bear. I had to take a stand, even if it meant getting decapitated with my own lunch tray.
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.