The 'racial' gap is easily explained by a few rather simple things. These things typically amount to 'generational institutional racism'.
Let's assume that pretty much every child is more or less the same in terms of ability. Now, take some segment that has an identifiable, but arbitrary trait. Let's use 'blue eyes' as the trait. Now let's put those children in homes with parents who are uneducated and who don't have any reason to respect the value of education. Make those same parents poor, and highly stressed. Let's make the quality of educational materials dependent on those same parents' ability to pay for them, which they can't. Let's make their teachers exactly those teachers who are forced into this ass end of the educational system. Let's put these kids in high population density areas, which because of their age, are rife with lead.
Then let's wait a few generations and tell ourselves it's genetic, because there is a population difference between the blue eyed kids and everyone else.
I submit that everyone is born in the normal population group, and the thing that primarily differentiates populations of students are culture and environment, and that this culture and environment has the capability of creating different kinds of intelligence, intelligence geared to different ends than the IQ, intelligence which helps the holder of it more adept at surviving with nearly nothing rather than intelligence which helps the person who possesses it build greater things.
I doubt African American populations in america are less intelligent, per-se, merely I expect that they have learned different ways of using their brains to get clever answers geared for the world we force them to live in as a society.
Edit: oh, look what I just found posted in Political Discussion. It appears to be a gorgeous affirmation of what I just said. THANKS Athena!
http://talkfreethought.org/showthread.php?9652-School-Segregation