This is layered... Not only will the kids grow up incorrectly believing that the earth is flat, they are also going to grow up resenting people that disagree with what their parents say, eventually they may even resent their parents for forcing their false beliefs on them and making them look foolish in front of their peers.
I have met a Flat Earth conspiracy believer mom who was homeschooling her kid, explaining how the sphere Earth model is wrong and so on, her complain was that despite her best efforts to indoctrinate educate her child, the child was not convinced that the Earth is flat. It goes to show that some children are just too intelligent to fall for this kinda shit. The child was eight or nine years old I think.
Reminds me of Aron Ra, he grew up in a mormon family, but in his case they waited with the indoctrinating until he was old enough, which was when he was eight
But as he himself said "by then it was already too late"
When his mother sat him down and started reading to him from the book of mormon, he just pointed out things that were wrong and stupid.
Remember, if you want your kids to believe the stupid things you believe, start early and don't let them see or hear too much about reality, or you'll have a bad time
Me, after learning where Mormonism came from: "So you're telling me your entire belief system stems from believing a teenager, who was known to be a con man, had golden plates given to him by God that nobody else was allowed to see? Are y'all fucking dumb or something?"