> have completely failed to predict future success when you remove confounding factors.

It seems to me that measuring/estimating the scholastic ability/preparedness of a prospective student has value independent of whether that preparedness is correlated with some other variables (wealth, neighborhood, childhood nutrition, other socioeconomic markers).

“Are they prepared/do they have the aptitude to succeed here?” matters much more than the underlying reasons why they might or might not be prepared.