As near as I can tell, if you grow up in the magical world (as opposed to be Muggle-born, for example), you do not go to school at all until the age of eleven. In fact, it’s entirely unclear to me how the children of the wizarding world learn to read and write. There is a reason Hermione seems much more intelligent than Ron Weasley. It’s because Ron is very likely completely uneducated.h/t Kottke
And even at Hogwarts, while they learn about spells and potions, they completely neglect the fundamentals. They are made to write essays on the history of magic, but are never taught to write. They take Arithmancy, but never learn mathematics.
There's some dispute in the comments over the education Ron received prior to Hogwarts, and whether wizards are in need of further education.