Not to be too much of a pedant, but: Turkish-Germans make up only 2.1% of the German population and while France doesn't have hard numbers because it's illegal to survey on the basis of race/ethnicity, estimates are around 7% of the population.

American blacks make up nearly 13% of the population in the US. That's a pretty significant difference and if you include all minority groups, America's a significantly less homogeneous place than any country in Europe or Asia that I'm aware of.

I agree with your (unstated) premise that this isn't the point, though.

Actually, to be more precise, the difference in Pisa scores in Germany is not exclusively turkish, it's between people with "Migrations-background" and people without. I.e, ethnic Germans vs non-Ethnic Germans. According to this article, the difference is 56 points now (http://www.spiegel.de/schulspiegel/wissen/0,1518,733188,00.h...). It was 90+ points previously.

Non-ethnic germans make up 20% of the population, far greater than the 2.1%. See here: http://de.wikipedia.org/wiki/Deutschland#Demografie

Same goes with France, I just used 'arabs' for demonstration, but the actual non-ethnic French percentage is higher than the ethnic blacks in the U.S.

Well, clearly this means moving to Germany makes you stupid. Being born in Germany clearly provides some kind of immunity.

Or am I drawing erroneous conclusions from the data?

1. Some/many (?) Germans do not accept all children born in their country as native Germans. So a person with 'migration-background' may be born in Germany, but one of the parents has immigrated. 2. I interpret the PISA data as: If parents have a low education, then in Germany their children will probably get a low education, too.

American Chinese vs Chinese Chinese is the only fair way to do this; otherwise, it's apples and oranges (and oranges are better).

No way. American Whites vs Chinese Whites is the only fair comparison.