Is it true that Shakespeare’s wife could not read?
If so, she shared that attribute with about 80% or more of the general population of the time. While it’s ironic to think that the wife of the greatest English playwright was illiterate, so was almost everyone else, making it not that terribly unusual. It was the literate person who was more remarked upon.
Near-universal literacy in the West is a 19th-century phenomenon.
I believe girls had much less opportunity than boys to go to school, anyway.
I have heard that at the time even women who knew how to read usually could not write. Most people saw little enough reason to teach a girl to read, and almost none at all to teach her how to write.
Lamia is correct that the concept of literacy is more complex than we might assume. Reading and writing are different things. Moreover, it is not easy to measure either for late sixteenth century Englishwomen. Just about the only precise measure historians have is the percentage of the population who, when required to sign a document, did so with a signature rather than a mark. This is not a true measure of writing ability as their name might have been the only words some of these people knew how to write. IIRC, there is an example which shows that Anne Shakespeare signed documents with a mark.