Our kids, Christian (24) and Erin (17) were both diagnosed as "learning disabled", after having a great deal of difficulty learning to read. We had them placed in the "resource" program at their school, and they did eventually learn to read. They both were reading past their grade level by the time they finished high school.
Since the two older ones had such problems, we just put Casey right into a program at her school called "Powerline" when she first started Kindergarten. She is going into second grade now, and reads past her grade level.
"Dyslexia" is kind of an over used term like "cult". It's used to describe so many things that it almost doesn't mean anything anymore. A lot of people assume it means that the person sees letters backward. If it were that simple, they would just learn what backward letters looked like, and get reading. It is more complex than that, and has to do with the decoding mechinism in the brain.
I would sit and watch Christian struggling with math problems. It might be 4+2. He would stare and stare at it. Then I'd say, "Christian, what is four plus two?". He would immediately say "Six".
He knew the math, he just couldn't get his eyes to work with his brain when it came to written symbols.
The important thing is to have your son tested by someone who is trained to diagnose learning disabilities. Once they pinpoint the problem, they can work with him and get him reading. Often Public schools have people who can do this. If not, you may have to find an outside resource.
The thing is, the older we started with the kids, the longer it seemed to take them to get over it. Christian took almost until his last year of high school. Erin got it under control in middle school, and Casey started reading well in first grade.
In my experience it can be ovecome, but not by traditional teaching methods. It really takes someone who is a specialist in learning disabilities, and these people seldom use the term "dyslexia", more often they describe the problem has having to do with fine motor skills.