Here's two studies that tested for heritability of IQ.
IQ test predict performance with the same self-identified racial groups, so what explains that?
No source here so I can only assume where you got this data. The most commonly cited source for this is the one used in The Bell Curve which compared test scores of black children in America immediately post segregation and apartheid South Africa against white American children. So, like, obviously the segregated underclass in two deeply racist countries is gonna have a lower quality of education.