I've been reading a bit about the history of education in the U.S., and I find it interesting that the Puritans were the first to really push it. Why? Because if you couldn't read the Bible, Satan would getcha!
Here's a cool link to info on the first education law in the country (Massachusetts Education Law of 1642). The INTENT of that law is, I think, what homeschooling parents strive to do: help them become literate, functioning members of our society (and then some).