Berolina - I noticed on another thread you mentioned about HE being illegal in Germany, and it reminded me that I had seen this article when looking into internet schools.
Educating service children - specifically the 5th box down, where a British service man in Germany is using an internet school for his daughters.
I don't know whether whatever loophole applies to this family is of any relevance to you, or whether an internet school would appeal to you anyway, but as I say, your comment reminded me about it....