How long would it take for a teenager to learn how to read?

I'm currently plotting a novel in which the MC is a street urchin living in a deep slum. One of the challenges I want him to face in this novel is learning how to read at the spry young age of 13. But alas, I cannot find any sources on how long it would take someone like this to be able to read a high school level text book.

He's pretty intelligent, but has never had any formal schooling. He's being taught by a librarian in (mostly) daily lessons of 1-2 hours in length. He can recognize most letters, and knows the sounds that some of them make. He can also recognize certain words from their shapes; mostly sign words such as 'STOP' and 'PARKING' and 'OPEN' and such.

Any suggestions as to how much a boy in this position would actually know are also welcome. I'm completely ignorant on the subject,

http://www.worlded.org/docs/Publications/teaching_adults_to_read.pdf

Page 9, 12, etc.

200-300 hours of instruction. So, by your timeline, about 100 sessions. So, anywhere from 3 months to 2 years, depending on how often he goes.

Here's another thread on the topic http://www.nanowrimo.org/en/forums/reference-desk/threads/42172