That sounds more like he knew the subject (literature) rather than knowing the material (n'th grade literature). In my experience the people best equipped to do

That sounds more like he knew the subject (literature) rather than knowing the material (n'th grade literature). In my experience the people best equipped to do something like that are people that have knowledge beyond the class they teach - the high school teacher that has a phd in the subject they are teaching, the university teacher that is currently involved in research etc. Especially in physics and mathematics I think this is relevant, as there are many times where questions naturally lead into topics from a much more advanced level. Like say the teacher explains that 3 isn't divisible by 2 and someone pupil says it is in fact divisible and the answer is 1.5. A teacher with solid knowledge of abstract algebra, that knows peanos axioms, and how Q is constructed from Z will be better equipped to deal with that. On the other hand I could see how teaching one and the same class over and over might lead to a bored teacher and a narrow perspective.