> It seems far better to have the incredible teachers leveraged as far as possible

And your assumption is that the potential leverage is quite big. I doubt it: I've seen many students profit a lot from 1 on 1 private lessons - from students 2 or 3 years ahead of them (or even from the same class). They are arguably nowhere near as good as a teacher who has studied teaching and has years of experience. Yet they can help the student a lot more because they can focus 100% of their time on the single student and his individual needs.