I got your point, but I think that the problem is not "helping" (with scholarships) based on membership with minorities, but helping when there are bad economic or social conditions. This may be correlated with other attributes yes but I think that we must write rules for persons by only considering the factors that effectively prevent them from studying and not the skin color.
If you agree that there are hidden mechanisms that shape the inequality, then claiming that “only considering the factors that effectively prevent studying” is fair would require a great deal of certainty in knowing these factors. I don't know how effective “positive-discrimination” is in practice but to me it seems that its principle is to do what you say but with discriminatory features as a proxy heuristic for these “effective features” (this makes sense if you believe they are sufficiently immesurable IRL).
