Along those lines... your thought experiment...
A thought experiment: take two schools, one low-performance and the other high-performance, and leave them exactly the same except for switching the student bodies.
How about moving all the teachers?
Put all the teachers from the wealthier, parent-caring, self-sufficiency/achievement culture, high performing school into the mostly thuggier, single parent, victimhood/dependence culture low performing school.
Irrespective of outcome [which I think can be easily predicted] there would be a lot learned.
I agree, of course.
My point is that any school is dominated by its students, at least if the administrators allow them to.
Turning around bad schools in the ghetto would require FIRST the imposition of discipline. This is impossible in a world where coming down like a ton of bricks on black students, regardless of their behavior, is politically unacceptable.
I suspect, without actual facts to back me up, that <5% of thug students will demoralize an entire school. In many ghetto schools, I suspect the percentage may be above 50%, though a good many of those are salvageable, only imitating the real thugs.
To turn these schools around, the school would first have to idenfity and expel the real thugs, then concentrate on instilling discipline and middle-class values in the remainder, and then teaching MIGHT become possible.
Since every single one of these steps is non-PC, it will never happen. We will go on pretending the issue is money or the building or the teachers. And it just isn’t.