I've come across similar data comparing school districts across the state of Texas. It graphs school districts' academic performance against the percent of economically disadvantaged students. The data used is different from what I used for the RISD graph, but the same familiar pattern is there. As socio-economic status drops, so too does academic ranking.
Source: Children at Risk.
Digging up a post from 2016 in which I showed a graph using national data, the same pattern is visible again (graphed in the inverse this time). As socio-economic status goes up, so too does academic ranking. RISD is the red dot, near the top for its socio-economic status (Yea, us!).
Source: New York Times.
No matter how you look at it — local, state or national — the correlation is the same: academic performance tracks socio-economic status. Demography may be destiny, but we still need to do our best to educate everyone who walks in our doors. We still need to constantly improve our teaching methods, materials, and facilities. But we also need to find ways to address the socio-economic differences that drive so much of the outcomes of public education. School districts have a role to play there, too.
I don't have the data to prove it, but I believe that outcomes improve for students from lower socio-economic classes when they are in diverse classrooms, without negatively affecting the outcomes for the students from higher socio-economic classes. If that's true, RISD needs to examine everything, particularly its school attendance boundaries and its magnet schools, with this in mind. Magnet schools can't be lauded for having high diversity if it's achieved by leaving the abandoned schools with less diversity. Keeping school boundaries intact for decades can't be defended if schools on either side of those lines are becoming more and more segregated in different directions. I don't pretend to have all the answers. Heck, I don't even pretend to have all the questions. But just from my perch in the bleachers, it seems to me that the RISD isn't having all the dialog that's needed on this subject. I hope that changes.