To be able to learn something, you have to have reasonably understood its prerequisites.

I'm not sure if I understand this, but at face value I disagree with this. For example, there is evidence that infants start learning gender roles as soon as their eyes can focus far enough away to be able to see what all is going on. This is a great example of "the things you assume which really sink into them", and I'm not sure what the understood prerequisite would be.