A stutter is a disability not a sign of lack of intelligence/education.
In other words, he was 17 and couldn't read fluently. But he wasn't stupid. He was quite conscientious about his side business and bookkeeping.
ps: I stuttered when I was a child.
I've read and written in English everyday for 10 years. I just can't speak it. One day I realized most news article I read were only translations of other articles. So I decided to skip the middle man.
Is that your professional medical opinion?