My guess is that all the principalities in Germany, considering it is a constitutional issue, left the devil details to the national lawmakers to decide, instead of their own local governments.
Although it could also be a case where the language used at the national level does not filter down to the local level very well.
I live in Germany so I can speak to part of this. State governments are given an enormous amount of latitude on schooling. The national gov’t can dictate a few things but it’s state funding, not national funding, that provides operational cost.
I also think there’s more than enough regulation over private schools in existence. What this foundation is attempting to do or say....is force some national authority over what states run. It won’t happen because all sixteen German states would laugh in the face of the Berlin authority.
As for private schools and immigrants....zero potential. The state-run public schools are the only device existing. I do think that in some major urban areas....some Islamic private schools might attempt to exist but if you look at what states wrote as regulation....you have to have a university degree and I don’t see these Islamic charity units coming up with enough cash to fund this type of operation. Most new immigrants will never have the cash to pay for even part of this financial cost.
As for the success of these private schools that do exist? None of these are cheap or “affordable”....but these private schools or academies do turn out bright kids. Part of their success I think...is that they have lower ratios of kids to teachers.