One could claim that that's due to different gene pools but if that were the case, one would expect to see schools which have homogeneous populations to be similar to their home countries. But one doesn't see this.
I don't know if we see this for homogeneous schools or not, but I do know that on things like PISA scores when broken down by ethnicity, American students do reasonably well compared to the countries from which their ancestors came from.
Asian Americans outscored every Asian country, and lost out only to the city of Shanghai, China's financial capital.
White Americans students outperformed the national average in every one of the 37 historically white countries tested, except Finland (which is, perhaps not coincidentally, an immigration restrictionist nation where whites make up about 99 percent of the population).
Hispanic Americans beat all eight Latin American countries.
African Americans would likely have outscored any sub-Saharan country, if any had bothered to compete. The closest thing to a black country out of PISA's 65 participants is the fairly prosperous oil-refining Caribbean country of Trinidad and Tobago, which is roughly evenly divided between blacks and South Asians. African Americans outscored Trinidadians by 25 points.
You might want to be careful about posting links to VDARE, lukeprog and some others here consider this crimethink.
I haven't studied these issues, but I will note that Steve Sailor and VDARE.com are considered by many people to be racist bigots. Here, for example, is a VDARE article defending white supremacy:
One of the many reasons I have been spending less time on LessWrong (sic) recently.
Post by fellow LW reader Razib Khan, who many here probably know from the gnxp site or perhaps from his debate with Eliezer.