When my oldest son was five, he hated the idea of me teaching him anything. He didn't want to learn his ABCs, how to write numbers, or anything else. So he spent a year in public kindergarten, learning what his alternative would be if he wouldn't let me teach him. And he chose to be homeschooled after that.
Now, I have another five year old, my youngest son. And some days I almost wish he didn't want me to teach him. Almost. But mostly I am awed and amazed by how quickly he picks up on things. He just turned five in December, which means if I were sending him to public school he wouldn't be allowed to go to kindergarten until this coming fall. However, here at home, he is doing first grade work, and blowing through every workbook I get for him in a matter of weeks. He's doing simple addition and subtraction and just started doing two digit addition.
As far as reading goes, he is on the same level as my seven year old (who admittedly is behind where I'd like him to be, but I learned with the oldest that you can't force somebody to read). He often will read something on a sign or a book just by using the phonics skills he is learning. He is hungry for knowledge, and it's an amazing thing to behold.
My biggest problem is that he won't leave the school room. He wants me to teach him all day long. And I have to get him to understand that as much as I love seeing him learn, I'm responsible for three other boys and their schoolwork, too. I can't spend all day with just one of them. Next year my oldest starts high school and it's only going to get harder to cram all four of them into each day.
All I can say is that I hope I always have this problem with him, with one change - that he'll work on it independently!! If he can do that, he can go through as many grades as fast as he wants. And I can work with the boys who actually need me sitting right there with them or they don't get their work done.