Note: I do NOT agree with this premise!
It is supposed to be a CULTURAL bias, not an economic one. Even rich black kids don’t understand white culture.
Of course that would mean that Asian kids would score poorly because they come from an entirely different culture...
Yep. Any excuse which blames "culture" must take into account the Asian kids being able to get good scores, despite being from cultures that are very different from Western culture.
There was also the Minnesota Transracial Adoption Study, where black kids adopted by upper-middle-class white couples, brought up EXCLUSIVELY in white culture and educated in middle-class schools, did not do significantly better on IQ tests than the black norm.