Woah there. You've extrapolated a number of things that I never stated. Let's revisit this:
'but while it is hard to generalize, there is a strong
tendency'
I went out of my way not to generalize. I stated a tendency. There is no hard and fast rule here.
'The truth is that most muslim women in Germany,
especially the Turkish ones, don't even wear a
headscarf.'
I did not mention headscarves. Not once. I stated 'misogyny'. The two are not the same.
'I almost never hear "Multikulti" except from extreme
right-wing people, and those who share racist opinions,
but don't consider themselves Racist.'
"Multikulti" was a concept was popularized by the liberal Alliance 90/Green Party. Merkel, of the right leaning CDU stated multi-cuturalism has "utterly failed" back in 2010 [1]. This is a partisan concept. I therefore struggle to see how you can associate the attempt by the German people to have a multi-cultural society as racist. I don't understand how you make that connection?
'There is a well documented effect in that the teacher's
expectations are reflected both in subjective grades and
objective performance.'
That I agree with.
'Another confusing factor is that most Turkish
"immigrant" children are anything but immigrants. Their
parents or grandparents immigrated to Germany decades ago
and helped build the country.'
Agreed, these children come from a migration background. I should have made that clearer. My observation was that specifically the boys have a problem with women teachers telling them what to do. This includes female teachers that come from a "Migrationshintergrund". Women having a position of authority over these boys is a problem for them.
'pin this complex problem on a mysterious genetic factor
that makes Turks dumber'
This one baffles me. I stated that these boys have a discipline problem. I also stated that these children are not achieving their potential because of the misogyny,
not because they are dumb.
Bottom line is that a misogynistic cultural attitude is prevalent in Turkish society. That misogyny concerns the role of women in the work place. It especially causes problems in schools where women teachers hold positions of authority over young men who do not like, and are not used to, that scenario. As a result come discipline problems that (as you so eloquently put it) 'the teacher's expectations are reflected both in subjective grades and objective performance' results.
It is a vicious cycle. Hence, I went out of my way to state that both sides are to blame. You appear to have overlooked that fact.
[1] http://www.bbc.co.uk/news/world-europe-11559451