Of course it's hard to tell if allowing arbitrary exceptions also allows the same kind of problem. "I'll give you a warning because [you're white and] you're normally a good kid and one mistake shouldn't ruin your education"
As illustrated above, there are always arbitrary exceptions, because the people can informally let kids off the hook. The problem is that the punishments are so high. Why can't zero tolerance use less drastic punishments?
You seem not to have read my post. The reason it exists is to allow the arbitrary destruction of kids lives, preferentially as a weapon against minorities, undesirables, the poor, often all of the above. You're treating the primary purpose of that feature as if its a bug. Like asking why the "rm" command takes the drastic effect of deleting files.
For example, one reason why it might exist is so if a teacher gets called a bitch, the cops would laugh at a teacher who tried to report that as assault, but if the teacher can label a girl as a drug dealer and get her expelled and prevent her from graduating or getting on the middle class treadmill in general, because of the girl's monthly cycle and some advil in her purse, well, we'll see who's the dominant primate and who gets the last laugh in that argument. Its NOT a bug its an intentionally inhumane feature, correctly implemented.
Its possible to do a really efficient and effective job of being evil. I don't really know how to rephrase it more clearly? Its like the anti-google motto or something?
In situations where there is no "zero tolerance", there are still arbitrary and gross executions of power, but the agency behind this power can at least be (more) clearly traced to the actors behind it.
I didn't respond to your post. But you are wrong about the reason "it" exists. The school administrators that create the zero tolerance policies are usually not the same people that are on the ground enforcing the policies. It might be used as a weapon by the teachers on the ground, but they aren't the ones creating the policies.
Getting declared "gifted" can give you massive amounts of privilege.