Seiner bescheidenen Meinung nach sollten dieselben unproduktiven Popularisatoren, denen man den Unterricht an den Mittelschulen anvertraue, die Lehrkanzeln an den Hochschulen besetzen, damit die eigentlichen, wirklichen, schoepferischen Forscher sich ausschliesslich ihrer Arbeit widmen koennten.
In his humble opinion, those same unproductive popularizers to whom middle-school instruction is entrusted ought also to occupy university podiums, so that the real, true, creative researchers could devote themselves exclusively to their work.
You've understood everything fine, don't worry. My suggestion is only an alternative.
Meiner Meinung nach, seiner Meinung nach, etc. are fixed phrases, with the preposition after the noun just out of custom.
It may depend on the time and place how you ought to understand Mittelschule -- one of my dictionaries gives it as either a casual word for Realschule, which is more like a non-college-bound career high school, or a Swiss/Austrian word for any secondary/high school. But a middle school is a modern North American junior high, so I doubt that's quite right.
Kanzel literally means pulpit, but I have the feeling here it means a podium, lectern, platform, etc.: the place from which a university teacher lectures. If this was from a time when most university teachers were still clergy, however, it could be literally a pulpit, or it could have a slightly different usage in Swiss/Austrian German or older German.