> So, there are clear efficiency and quality gains to be had if the system is specialized.

I'd agree that "specialization" is a good thing when it means that educators have the training needed to most effectively deal with other-than-typical circumstances. But it may be less of a good thing when it means segregating those students into their own classes or their own schools, which I think is what GP is saying effectively happens with charter schools. Setting aside the cost argument, giving students a chance to interact with and befriend those with different backgrounds, circumstances, and abilities benefits the students and society, though it may not be reflected in standardized test scores.