I believe if you teach a kid from birth that the earth is spherical, that is what they will most likely believe that it is until they die, just as if you teach them if its planar that is also what they will hold through a lifetime.
I think a small percentage of these kids will question either theory, do research, perform their own experiments.
The kids are Zetetics, and they are our future.
You have a very small view of kids and adults.
It is true that, if you are a farmer in medieval times, you will hear someplace that the Earth is round, or square, or triangular and you will believe it for the rest of your life. But if you are a reasonably well educated person in current times and you hear about a hovering Sun, you ask questions.
You ask why Einstein thought Mercury orbits the Sun at enough speed to have relativistic effects, while Rowbotham's Mercury is exactly as fast as the other planets. You ask why the Sun sets in the West and not the North West. You ask yourself what the Conspiracy really should do to get the whole world fooled.
In the end, evidence of a round Earth is far too overwhelming to deny.
What you FE'ers do is called a non-sequitur: you start from the true statement that most people would not be able to demonstrate that the Earth is round and conclude that people are being fooled.