The above is for a whole host of reasons, none of which is that Black people innately lack intelligence.
The writer speaks of different ways in which individuals and groups differ. Statistically, blacks don't do as well on IQ tests as non-blacks ALTHOUGH some 6 million blacks perform better on IQ tests than the average white. IQ tests generally reflect how well a student will perform academically.
Even though Shelby Steele is smarter than I would ever hope to be, as a white of average intelligence, I am, statistically, still going to perform better than most blacks. And most Asians will perform better than I. It's not a question of "lack of intelligence," but rather a statistical comparison of intelligence among groups that cannot be assigned to cultural differences alone.