Makes you wonder about the general population in Elder Scrolls games. Given how common books and random notes are, it seems like most of Tamriel is fairly literate, but even the game of Daggerfall, which had infamously large cities, didn't have any schools iirc.
Nor children, come to think of it.
New theory: In the Elder Scrolls universe, everyone is dropped on Nirn as a grown adult, skills like writing and trade skills intact. The children in Skyrim were clearly just Sheogorath playing a prank.
But in actual answer to the question... I've never really thought about it. Many of my characters came from upper class homes (and one was a ward of the Mages Guild) so would have had access to such education. I assume there is some sort of group schooling in small communities, even if it's just gathering all the village kids together for an hour a day between chores to teach them to read and count... so that would explain a few others. But then, I get to my ex-slave and my bandit, and I draw a blank. It's an interesting backstory question to noodle over, I think.