Just like death, stupidity can't be stopped. In a way we're all born stupid. But it's only we're unfilled. Children have space for knowledge. If not to fill it, immaturity becomes stupidity.
Children have the ability to learn.
After some time it ceases. In the life of a child there is certain moment, and after that he cannot learn more. When he will achieve complete knowledge, his education ends. Anyway, it may be the whole of a real virtue, or it may be the whole of some rubbish. It's the completeness of the path.