You’re probably referring to the fact that the school system differs from state to state rather than being organised at the federal level but I find that quality of education differs a lot more between individual schools than it does between states, and not just because of the tiered system (grammar would be elementary school curriculum anyway).

As someone who went to four high school in three different German states, I can assure you, that the state is a very good indicator. As a child, you live in a world of stress when you move from easy to hard and basically repeat a year, when you move back.