These policies most benefit good minority students. The majority of school infractions are committed by bad minority students. Bad minority students are almost always in schools that are majority minority, not majority white. That means that these troublemakers most impede other minorities from getting a solid education. But, hey, black people seem to have a thing for defending the dregs of their population even if it's at the expense of the good portion of their population.
The only thing the "zero tolerance" policies seem to do is make them develop selective tunnel vision. In order to say they enforce a "zero tolerance" policy on the students they want to punish they convince themselves the same behaviour by students they don't want to punish never happened.