I don't believe there's any such thing as a "black IQ" or a "white IQ," because racial categories are extremely unscientific. If you assorted people by 5 or 6 different kinds of blood types (not just ABO, but M, N, and other alleles) you would find a far different racial picture than the one we have that's based on skin color and hair texture.
Similarly, what we call "white" is really a broad group with some significant genetic differences. Some used to matter 100 years ago (like calling Jews a "race" and drawing a distinction between northern & southern Europeans.)
You cannot look at a black child and say, that child isn't going to do as well in school simply on the basis of his race. What you *can* look at are all the things that contribute to success in school, and IQ is just one. Far more important are factors like early childhood language development; are the parents married & stably employed; does the mother provide a language-rich environment for the child?
Obviously this kind of parental preparation of the child for school isn't racially determined - if "African genes" were that determinant, then black children should have far fewer problems with language in school (after all, Africa has been home for centuries to incredibly rich & varied oral language traditions.) White parents who raise their children in dysfunctional families with language deprivation from birth to age 3 show the same problems in school *and* in life.
What we need is an entirely race-blind school system, with every child treated *completely* on the basis of his individual educational needs, NOT on the basis of his race or income level. This means no racism; it also means no affirmative action or other special treatment. It means that teachers need help & support dealing with a *wide* variety of children, not just the "smart" ones. It also means that parents should be held to some pretty basic and minimal expectations, like get your kid to school properly clothed, fed, homework done, on time, etc. No one should be held to a higher OR lower standard because of his race.
If children are not being taught problem solving skills and/or logical thinking, they are not going to score as well on this test.
I'm not going to say the tests are "culturally biased", but a difference in culture does affect "what you know", and the test may be based on a different cultural "what you should know". Given that this basis is on what is expected in our society, it gives an idea of the ability to succeed. I don't believe it accurately reflects the individual's ability to learn.
The SATs probably are a better assessment in that they determine how well you will perform in a college environment and in society as a whole.
I welcome others' insight on this.