Their concluding speculations (on why less experienced/qualified teachers' students perform better now and worse later) omitted the two I've seen: (1) You're b

Their concluding speculations (on why less experienced/qualified teachers' students perform better now and worse later) omitted the two I've seen: (1) You're better able to teach if you've learnt it recently (say, within 5 years). This is because you remember what it was like not knowing it, so can better communicate with someone who doesn't know it. e.g. "demonstrators" (often last year's students) often communicate better than lecturers. (2) The paradox of excellent teaching is that students get less practice in struggling, working it out for themselves, finding other resources (peers, texts). They learn the material, but not how to learn. That is, spoon feeding is a form of "disabling help", where doing something for someone that they could do for themselves deprives them of developing that capability. Perhaps... extremely knowledgable but hopeless teachers are best.