My dd is one of those immigrant children mentioned by ZZen, stuck in teh Hauptschule in Germany. It is a bit embarrassing for the HS actually, as they now realise that our family is academically high achieving - eg I studied at Oxford, as did other family members etc. DD is clearly far too intelligent for the sort of future she is facing, but she just can't manage to get the marks to get out of the HS, and ZZ is right when she pinpoints the language as one problem (Another one is that the chidlren are required to study like A level students, aged 10). 2/3 of the marks needed to get to the grammar school are given on written subjects (German and social studies).
I am now getting strong pressure to transfer dd to the Wirtschaftschule to save their face, which is yet another kind of secondary school, and one which trains your children to do office jobs like book-keeping(eg, the children dont study maths, they study book-keeping). From this school, you can't go directly to University.
I don't want this, and neither does dd. Interestingly, the current school is ready to accept that dd will never fulfil her potential, but that if she stays in Germany, her children (2nd generation immigrants) will.
At the moment, I feel like making fools out of them by letting dd carry on in the Hauptschule, and transferring her to a private Gymnasium (grammar school) aged 16 to do the Bac.
I do know one immigrant child who got to the Gymnasium after 2 years in Germany. He is an only child, whose parents earn enough for tuition 5 days a week. He is also unnaturally studious for a 10 year old, the sort of child you could imagine being hothoused to A Levels aged 11. And yes, teh Hauptschule where dd is, is full of immigrants.