次の一節の２つ目の文についてお尋ねいたします。
All of this seemed to me unconnected with academic life, which I perceived as provincial, shallow and thin, a colourless, lightweight world unrelated to real life. I took university to be more or less a continuation of school, and professors to be the next level up of a schoolmaster, people who lived their lives in closed institutions devoting all their working energies to the same sort of subjects as were pursued in school classrooms: Latin, Greek, history, geography… I found these subjects easy to ‘do’, but had never seen much point in doing them. What seemed to me to penetrate life to the core - and therefore to be, ultimately, what living was for, in addition to relationships with other people - was the creation and absorption of works of art. Artistic experience, it seemed to me, was in a totally different category from any other sort of experience, except sexual experience, when it came to glory and significance. It was the distilled essence of living.
(- Bryan Magee, Confessions of a Philosopher, p.26)
関心のある第２文のみを改めて以下に引用します。
I took university to be more or less a continuation of school, and professors to be the next level up of a schoolmaster, people who lived their lives in closed institutions devoting all their working energies to the same sort of subjects as were pursued in school classrooms: Latin, Greek, history, geography…
この後半のpeople以下は、どのように解釈すべきなのでしょうか？
peopleの前にandはないのでthe next level up (of schoolmaster)と同格の関係にあると考えるのかなと思いました。一方、the next level up (of schoolmaster)の部分とpeople who以下の意味の重さが対等ではなく、後者が前者の説明（あるいは補足）をしているように思えます。このような関係も学校文法では同格の関係にあるというしかないのでしょうか？
基本として学校文法の枠内で説明するとするならば、どのような説明になるのでしょうか？ ご教示ください。
