This doesn't actually address any points I made.
It doesn't matter how many times you tell people it's stupid to believe in a flat Earth, if the Earth is flat then a lot of people are going to know it because it's not possible to do their jobs without that information. Yet all these people, who are ordinary people (not some kind of high level agent clearly devoted to the cause who is granted access to top secret materials) keep this going without revealing what's really going on despite not really having any incentive to. Similarly, nothing seems to be gained by this massive conspiracy despite all the effort that must be put into it.
People believed in a round Earth a century ago and for centuries before that. Maybe you could find a few fringe people who held otherwise, but the round Earth was widely believed in and taught.
You talked about what schools were teaching. Okay, here is a geography textbook, "Lessons in Geography for Little Learners" from 1889 for use in schools:
Right there it says "What is the shape of the Earth? The Earth is round like a Ball."
Looks like a century ago people
were teaching a round Earth in schools. Let's look at some other older books written for usage in schools from the last century or two.
Sadliers' Elementary Geography (1880):
72 p. 21 x 17 cm
archive.org
"What is the shape of the Earth? It is round like an orange."
Cornell's First Steps in Geography (1876):
Includes publisher's list
archive.org
"What is the shape of the Earth? The Earth is round, like an orange or a ball."
So it looks very much like they were teaching in schools that the Earth was round, even more than a century ago. Indeed, a round Earth was believed in--at least in the West--for centuries upon centuries before that. For just one example, Thomas Aquinas in the 13th century had this to say in his work Summa Theologiae:
Is it necessary? Is it a science? Is it one or many? Is it speculative or practical? How it is compared with other sciences? Is it the same as wisdom? Is God its subject-matter? Is it a matter of argument? Does it rightly employ metaphors and similes? May the Sacred Scripture of this doctrine be...
www.newadvent.org
"Sciences are differentiated according to the various means through which knowledge is obtained. For the astronomer and the physicist both may prove the same conclusion: that the earth, for instance, is round: the astronomer by means of mathematics (i.e. abstracting from matter), but the physicist by means of matter itself. Hence there is no reason why those things which may be learned from philosophical science, so far as they can be known by natural reason, may not also be taught us by another science so far as they fall within revelation. Hence theology included in sacred doctrine differs in kind from that theology which is part of philosophy."
Now, to preempt misunderstandings, I'm not arguing "Aquinas said it so it's true" (he got some science stuff wrong as he lived in the 13th century without some knowledge of subsequent developments); the point is that he not only believed the Earth was round, he took it so for granted he could use it as an example of how to prove the same thing in multiple ways. And this was back in the 13th century. Of course, it goes back farther than that--I merely thought Aquinas in particular was a good example because of how clearly for granted he takes it.
