I think a lot of the complaint about kicking out kids is that it tends to inflate the scores (by a lot). Kicking out every kid who misses more than 10% of the school year will by itself make you a decent school given an average start. So you can claim a lot of success that is mostly just exclusion of negative outcomes. Reasonable people can disagree on where that line is.

Notably too this is not how suburbs work. In that case the parents are choosing the flock, but the suburban district can’t remove kids easily. A lot of the benefit is just the kids are anything but average (i.e. very well resourced overwhelmingly not single headed and with high parental involvement) to start with. It still isn’t reflective of the quality of schools but the actor is the parents not the school.

That said there is some difference in charter kids vs public school kids/parents happening as well. It is complex though. A very good local public school diminishes charter school results because the parents aren’t incentivized to flee.

This stuff seems simple but really isn’t and at the high end is probably not actually even that important as the parents will do what it takes regardless.