Presumably once the downward pressure is removed, the oppressed group will recover, no? I am troubled by the impulse to see society as this simplistic set of oppressors and oppressed. It seems that almost every group got to play both roles at one time or another in various combinations.
And it seems weird to want to pay back a debt racked up by an ancestor. Or not even an ancestor, just an ancestor of someone who looks like your ancestors. Anyway, I don't think you help oppressed people like that, I think you help them by going in there and teaching and being positive about the real opportunities available - to go to college, get a job, earn a living. Live in a bougie neighborhood, maybe.