Also, are there special college courses he can get after high school to help him get a job and live a normal life?
In middle school, and particularly in high school, where grades tend to "count" more, the letter grades take on new significance. If a student has been earning high marks based on his ability to do his "personal best," and then he's tossed into the ring with all the other high school kids with the same standards applied, grades can plummet, and so can self-esteem.
If your son got good grades in elementary and middle school because he was given modified materials or took modified exams, the question is this: Were the tests and assignments modified to make them easier or more accessible? If a test is read to a blind student or to a student with learning disabilities and he or she gets all the answers right because he knows the material, then that's an "A" that equals other "A's". (Incidentally, you'd be surprised at how many people still can't understand this concept. They think that if a student can't take a test just like the other kids, then he deserves what he gets. Fortunately, these folks are in a minority.)
However, if learning materials or tests were modified by taking out every other question, or by simplifying the vocabulary or concepts, that's a different story. In high school, an "A" earned on that kind of test couldn't equal an "A" on an unmodified test. To make my point, I can relate a story of a young woman with Down syndrome, which is associated with some degree of mental retardation. Upon being awarded a national honor society certificate (based on the grades she got for "doing her best") the young woman turned to her mom and said: "What the honor society?" I can also tell you the story of a very bright and capable student with learning disabilities who told me he was afraid to go to college this fall because he had the feeling all of his grades were inflated by his teachers. The answer here is appropriate help, so that kids can do their best without having to struggle with the medium for learning.
Virtually all print materials can now be turned into spoken text, so reading disabilities are being re-defined by technology. Go to: http://www.cast.org and learn about an exciting product called WebReader. Teachers and parents must be honest with a child about his or her learning needs and skills, so that the student is not misled and then surprised or devastated when they "hit the wall" in high school (or college, or medical school, for that matter).