There are scenarios in life where we're all in this together and excising people for their inconvenience isn't what's best for society.
You don't just cast off disabled people into the void, for example. Unless you have a solution for where to put these problem public school kids that isn't juvenile detention, I don't want to hear it.
We're talking about children here. They don't know how to behave like adults yet. Cutting them out of society where they fail to meet expectations is cruelty.
I think you misunderstand what a zero-tolerance policy is and how it's applied. There literally is no tolerance. There is no nuance to them. If an incident is reported they are required to take action. There isn't a decision-making process past the point of the incident being reported. Everyone involved and any witnesses literally have to keep their mouths shut.
Adults are intentionally victimizing the majority of students to cater to their own shallow virtue signaling.