Here is a diagram of the German Education System for you to refer to as you read the reports of what is happening on this site.
You can see: the placement of the 'Sonderschule' (that 2 of the Gorber girls were to be sent to); that at 10-11 years the child's entire secondary education is decided by the teacher none-the-less; the levels at which the various certificate exist etc.

Full German Education System PDF, in English - 6 pages: 138KB
This comes from the Ministry of Culture who are ultimately responsible at Federal level for the education system. The PDF includes explanations of the terms in the diagram above.