A lifetime of people looking at you and reacting to you causes you to perform differently. Performance can change surprisingly quickly. Researchers have found that reminding people of their ethnic identity before they take a test will affect their performance on the test in accord with racial stereotypes. (Asians improve, blacks get worse.)
While it is politically correct to try to be colorblind, reality doesn't cooperate. You can be PC and pretend those effects aren't there. Or you can be intellectually honest and honestly look at how big an impact they have.
(That said, we can and should reduce the size of those effects. However we can't even begin to have a proper discussion of how to do that as long as we shoot the messenger that tells us that the effect is there.)
Hopefully not much. The visual differences simply demonstrate that they are separate and mutually distinguishable groups.
The numbers quoted in the main article demonstrate that these groups do differ in some characteristics which affect education, although they don't illuminate which ones in particular.
