I don't know how 504s work, but our DD also has dysgraphia and one of the psychologists recommended that the school accommodate her by letting her use a keyboard when possible and allowing her to answer questions with short answers rather than complete sentences when possible. She also advised that we look into the use of dictation software for homework, although we could not get it to work for DD's voice at this point (there are other threads on that somewhere). Also I guess I would try to get your son extra time on tests especially if there are essay questions.
