I think that the following quote from the WaPo is a pretty important clue:
In Maryland and Virginia, as in many other places, one of the most common causes of student suspensions are what many call “soft” — or discretionary — infractions: disrespect, defiance, insubordination, disruption and foul language.
I think this relates back to what Dale Carson wrote in his book Arrest-Proof Yourself about why redneck whites don’t get arrested as often as blacks:
Although low on the social food chain, these characters [redneck whites] don’t have a chip on their shoulders about race. They are less likely to act out in the presence of police. Generally they can stifle the profanity during those crucial minutes and mumble “Yes, officer” and “No officer” until the heat has passed.
Thus we see a pattern emerge in which whites, more so than blacks, are able to be polite and respectful to authority figures when they need to be.
I also believe that schools need to train low-IQ low-future-time-orientation students to be more polite, as part of the training in middle-class values. Unfortunately, the educational system is 100% laser focused on the gap in reading and math scores and doesn’t care about middle-class values training.