CathInfo.com

Are you sure?  They always taught us in public school that people used to think the Earth was flat, especially at the time of Christopher Columbus.  

What you got taught in public school was basically anti-Catholic propaganda.  I bet they didn't teach you that the Crusades were justified or give a fair explanation of the Spanish Inquisition either.  

The Spanish Inquisition is often cited in popular literature and history as an example of religious intolerance and repression. Some historians have come to conclude that many of the charges levied against the Inquisition are exaggerated, and are a result of the Black Legend produced by political and religious enemies of Spain, especially England. https://en.wikipedia.org/wiki/Spanish_Inquisition

There have already been lots of posts in this subforum explaining this in detail.  We know that that this story about belief in flat earth at the time of Columbus is false.  We have a pretty good idea of how and why the myth was spread and even published in school books.  

I am aware that The Spanish Inquisition, which lasted for over four hundred years, was for the legitimate defense of Spain and that the Inquisition strove to be quite fair and the actual numbers of executions and aquitalls reflect that.  I am also aware of English/Protestant propaganda in regards to The Inquisition.  However, I am not aware that The Flat Earth story is the same thing, particularly since The Bible depicts a Flat Earth.  I mean just because Protestants and The English used The Spanish Inquisition to defame Catholics, doesn't mean it didn't occur.  So, I doubt this question is as settled as you say.  However, I am interested in reading other threads on the topic and would apprectiate any suggestions.

The claims that Catholics at the time of Columbus believed in a flat earth are even less true than the claims about the Spanish Inquisition.  While Catholics disagreed on the shape of the earth during the Patristic period we had reached a consensus that it is a sphere long before the time of Columbus.  St. Bede wrote an influential work teaching the earth is a sphere around 700 AD and this remained the position of educated Catholics from that point on.  St. Thomas Aquinas and St. Albert the Great taught it.  The Church-run medieval universities taught it.

The majority of Catholics throughout history have not believed that Scripture teaches the earth is flat.  St. Augustine, around 400 AD, taught the Scripture is silent concerning the shape of the earth. So did St. Basil.  This is the view that spread through the Church and was eventually incorporated in a papal encyclical.  Catholics believed it was a matter to determine through science, and that is what St. Bede, St. Thomas, etc. did.  They all believed that science showed the earth is a sphere.  (Of course, you are free to disagree with them about science, if you want.)

The idea that Scripture teaches a flat earth comes from Protestants and is not the Church's interpretation of Scripture.  So we are not free to claim that Scripture teaches the earth is flat.

Here is a post with more detail about Columbus:  https://www.cathinfo.com/the-earth-god-made-flat-earth-geocentrism/did-catholics-before-the-'reformation'-believe-in-fe/msg581137/#msg581137

And here is a post with more about St. Augustine: https://www.cathinfo.com/the-earth-god-made-flat-earth-geocentrism/the-shape-of-the-earth-is-not-important-to-the-faith/msg612710/#msg612710

I was taught in public school that Columbus proved there earth was not flat, but round, and there was ZERO mention made of the Catholic Church at all.

It could certainly be argued that public schools like broken clocks are correct twice a day.