Imagine a free university, in which anyone can attend the first level class of any subject, without registering. There would have to be multiple sessions of the popular subjects, but in general everyone could come and listen to a professor “teach all in mediocrity”.
The purpose of these classes is not to instruct, but inform. Those who are interested will listen, and those who are not will move to a different class. In this tier of the university there are no grades, no examinations. People just come and listen, if they want to.
The second tier of instruction would require that students to pass an examination to enter the class. In these classes, a different kind of professor (and likely, a different person) would begin instructing his students in depth – knowing that his classroom contains only those interested in the subject, for whatever reason.
In this way, teaching in mediocrity serves the purpose of revealing interest – both for the academic institution, and also for the students themselves. People would be exposed to everything, given a taste of every flavor, so that they can discover their natural aptitude. After all, studying a beloved subject is a true joy, and I’d hope that even the student’s parents would allow each child to pursue whatever was his greatest interest.
Having found that interest, the student will naturally want to go into greater depth: just like your interest in English grammar. In this case a special professor is needed who loves to talk about the subject in great detail, and wants to take the students fully into that world. Now it is a joy for both of them, since the student wants to learn, and the teacher is excited to teach. This is teaching “a few but well”.
And there will be some who don’t like learning at all, who could pursue vocational opportunities. These would employ a different kind of teacher, more of an old world “master taking apprentices” – so that the same structure of learning takes place.
I think the dichotomy of “all in mediocrity” or “a few but well” shows a flaw in our current educational system, because we think it must be one or the other. Perhaps society itself is not ready to admit that some of its sons and daughters are not suited to study the more lucrative subjects. When there is greater respect for interest and love – and how profoundly these contribute to one’s capacity to learn and perform in society – then perhaps there will be room for both kinds of instruction, and the dichotomy will disappear.