What upsets me is your claiming St Bede mentioning sphere earth "almost in passing" is a teaching (which implies an undebatable, you-have-to-accept-this, fact). Instead of the word "teaching" you should use the phrase "proposed theory". Even then, a theory which is only mentioned in passing is quite worthless as a teaching tool.
Almost everyone was taught from the same textbook for centuries.
The Church never considered it a fact, so it's wrong to use the word "teaching". It was a theory open for debate. The Middle Ages was all about the Scholastic Method and debate. Something which is debated is not a "teaching".
Schooling today is basically indoctrination - here is what is true, memorize it, no discussion. That was NOT how the Middle Ages worked. They used their minds to actually think, not just memorize. Teachers in the Middle Ages didn't read from a book while students just sat there passively. Teachers would propose ideas, students would debate and argue and it would go on and on until something was proven. This is why the Dominicans came to blows against the Franciscans over the Immaculate Conception debate - things got heated;
there was not passive learning like we have today.