Large Percentages? Care to define what a "large percentage" is?
The UK, as an example, only has .025% Muslim population. That's it. We import more Latin-American immigrants EVERY month. Do you realize that the ENTIRE non-white population of Great Brattain is just under 8%? That's ALL non-whites.
The overall percentage in France is about 10% and 6% in Germany. The numbers are lower elsewhere, but rising across Europe. Regarding the UK, your figure is off by more than an order of magnitude, but the percentage is below France, Germany, and some other countries.
Moreover, the fertility rates of the Mooselims exceeds that of the native population. Consequently, the number of students from Mooselim families significantly exceeds the Mooselim population as a percentage. In addition, the advanced European countries have seen a large influx from much poorer Balkan and Eastern European countries.
Leaving all of this aside, our best students have done worse in math and science comparisons than our average students. Moreover, as Thomas Sowell has pointed out, the ABSOLUTE number of students scoring above 600 and 750 on the SAT verbal tests declined by almost 50% from th e60s to the 90s. This is why the SAT was renormed in 1995 - to “hide the decline” ;-)
The main problem is the government school system.