Remarkable how you jumped from 'IQ is largely genetic' to 'Turkish children remain at the same poor level that their parents achieved in the tests'.

Don't you see your the mistake in your reasoning there?

Probably that too can be explained by genetics or maybe by a failing education system but the point is: there are very dumb Germans and very smart Turkish people who would still score different on an IQ test in German. Especially after going through the German school system (which of course would never discriminate against children with a different ethnic background /s) and so on. The confounding factors at play here make the whole comparison without accounting for those factors utterly meaningless.