I'd be interested to learn about parents who continued focused eductions throughout childhood. While I can see that entering a public school and knowing to read won't give a lot of benefit since the child would be held back by the other students catching up, if the parent homeschooled or similar, the child may be able to continue accelerating. I'd also be interested to know if children who learn early develop better habits for learning, and therefore can learn new subjects more easily. Even an increased interest level in reading has benefit though, and I suspect a child who can read can find entertainment in books and that seems like it may help them as well.