Not really sure if this has been said before. But many teachers are marking wrong the answers kids come up with even if they are right because the way the answers were "realized" was wrong.
This brainwashes people by changing their way of thinking while they are kids. Instead of asking kids to discover a way to find the answer, they are telling kids that the answer must be found by using a specific method. They mark wrong any other method used to find the right answer, which shames and humiliates the kid.
As a kid being told "you're wrong" even though you're right and giving punishment has a severe and negative influence. It will end up limiting critical thinking skills, and also teach kids to obey authorities more. Similar methods are used in the army during boot camp to teach people to listen to orders and respect authority, they are always told they are wrong and never question orders given.