Earlier quoted context omitted.
You sidestepped my point. Segregating all the underperformers into one place causes harm and you're ignoring that harm, assuming that the benefit of segregating the high performers is more important. And you are in fact crediting the charter school with the benefit while ensuring that public schools receive blame for any harm that results. I think you're actually arguing against universal instruction, that we shouldn…
I don't think I'm ignoring the harm. I am accepting it. We can get into the utilitarian calculus, but before even considering that I don't think it's acceptable to force students who want to succeed into classrooms with those that don't. And really that's the end of the story for me. Maybe the total outcome is worse because the kicked out students cause much bigger problems than they would otherwise but that doesn't…
Now you're ascribing a specific cause and moralizing, assuming that it's harder for some subset of students because they want to fail, and that they deserve to fail. The utilitarian calculus does matter, you feel fine dooming some set of kids to a poor education because you think they deserve it.
No child deserves a poor education. We do have to choose who we prioritize and I don't really think your analysis of who "deserves" more help is sound.