I can see where this article is coming from. Inequality in educational attainment can translate into inequality in incomes. If people from poor households have lower educational attainment then we have a generational link between low incomes, which implies lower income mobility. This is something that we may find unjust.
Why do I say “may”, well this depends on the cause doesn’t it – why does this inequality exist.
Now I don’t disagree that educational attainment is associated with income inequality, and the narrowing of gaps in educational attainment has been associated with lower income inequality. I also don’t disagree that, looking at a person in isolation, lower mobility can be associated with lower opportunity.
But I am from a low income area and I am not sure we can blame universities for the fact that they primarily have students from higher deciles.