The learning gap in Guilford County, NC

A study by Guilford County Schools shows that the poorest white students scored higher on the SAT this year than the wealthiest black students. Gongsue Zhang, a statistician employed by GCS said he suspects the disparity comes from lower family and peer expectations among black students and possible bias in the SAT exam. This information brings about the following questions:
•Is the SAT culturally biased?
•Do black students generally have lower family and peer expectations? Explain.
•What, in your opinion, is the reason for blacks performing worse on standardized tests?