My anecdote is that I went to a charter school that served 23 different communities across basically half the state of Massachusetts. Median family income from these communities ranged from $54K (Leominster) to $202K (Lincoln). And there were very noticeable differences in both behavior and academic achievement between students from the Fitchburg/Leominster/Ayer region (poorer and more blue-collar) vs. wealthy Boston exurbs like Lincoln, Carlisle, or Bolton. Almost everyone at the school was white, so this wasn't much of a conflating factor (aside from some Asians & blacks adopted into wealthy white families, and half-Chinese like me who also were in relatively well-off and well-educated families).

Granted, it's a charter school, and my class was the first year they were legal in Massachusetts. This tends to exacerbate differences because you don't go to an experimental charter school unless you're unhappy with your existing school, and top reasons for being unhappy include falling behind classmates or being so far ahead that you're bored. But interestingly, a large number of those who struggled from poor districts went back to their home district, perhaps because they struggled even more when going to a school with a wide mix of backgrounds. This despite my school having a radically individualistic instruction method (every student had a personalized learning plan) and an enviable 1:12 teacher:student ratio.