If not a slave class, some other kind of under-class/race that was then declared equal under law. Are there any examples showing how long it takes such a sub group to "get over" the legal second class status of their ancestors, and catch up with everyone else in terms of education, income, public perception, general prosperity, etc?

In modern times, there are some groups that seem to have "caught up", and others that are still yet to fully recover. Blacks in America, for example. If you graph their average earnings from emancipation until now, it still hasn't caught up to the line for the general population. Nor has the line for life expectancy, or many of those other development markers.

Any examples from history showing how long that process normally takes?