Education is mostly about your peers. It's obviously true for prestigious universities but it's just as true for elementary schools. Charter schools kicking out problematic students isn't some loophole, it's the main point, and it absolutely can improve the education for those that remain.
My district has a quarter of high schoolers in charter schools. Almost all of them under the poverty line. It's not like they're only accepting kids with two parents, in fact they're doing a much better job of helping poor families in my district than the public school system, which forces all the poor students into the same schools with literal murderers attending. Allowing poor students from families that value education to go to schools with like minded students is an unequivocally good thing compared to what the public schools currently do.
My district has a quarter of high schoolers in charter schools. Almost all of them under the poverty line. It's not like they're only accepting kids with two parents, in fact they're doing a much better job of helping poor families in my district than the public school system, which forces all the poor students into the same schools with literal murderers attending. Allowing poor students from families that value education to go to schools with like minded students is an unequivocally good thing compared to what the public schools currently do.