This is a compelling biological argument that may be true in the case of the Ashkenazi. But I’m hesitant to believe that, on a larger scale, the impact of natural selection on the brain over mere centuries could really be affecting the achievement of racial groups so profoundly. The human brain, by and large, looks the same as it did hundreds of years ago. This is especially true in the case of the limbic system, which contains the true indicators of intelligence and cognitive function: the thalamus, hypothalamus, amygdala, and hippocampus. Disorders are different. When carried through smaller biological groups, the effect on intelligence of these disorders may be noticeable. But in the case of the achievement gap, where the correlation between race and performance is much more widespread, we need to look at fundamental brain structure, which is less prone to arbitrary mutation than DNA structure.

Although this is often attributed simply to culture, transracial adoption studies show that adoptees perform about as well as their biological peers, not their adoptive parents.

This summary of recent adoption studies on gene expression casts doubt on the idea that there is some unique cultural advantage driving these differences.

http://www.gnxp.com/MT2/archives/004064.html

In terms of the Ashknenazi there is evidence that local selective pressures exerted even over several hundred years can cause big changes in cognitive function.

“This paper elaborates the hypothesis that the unique demography and sociology of Ashkenazim in medieval Europe selected for intelligence. Ashkenazi literacy, economic specialization, and closure to inward gene flow led to a social environment in which there was high fitness payoff to intelligence, specifically verbal and mathematical intelligence but not spatial ability. As with any regime of strong directional selection on a quantitative trait, genetic variants that were otherwise fitness reducing rose in frequency. In particular we propose that the well-known clusters of Ashkenazi genetic diseases, the sphingolipid cluster and the DNA repair cluster in particular, increase intelligence in heterozygotes. Other Ashkenazi disorders are known to increase intelligence. ”

http://www.ncbi.nlm.nih.gov/pubmed/16867211

http://homepage.mac.com/harpend/.Public/AshkenaziIQ.jbiosocsci.pdf

The motives of a teacher in demanding excellence might be described as racist while actually being the opposite.