C.T.
L.:
Your son's personality is consistent with a "High C" in the DISC personality lingo. C stands for Conscientiousness. Persons with High C styles adhere to rules, regulations, and structure. They like to do quality work and do it right the first time. High C people are careful, cautious, exacting, neat, systematic, diplomatic, accurate, tactful.
Other ways of looking at personalities include psychogeometrics which translates personality types into shapes(your son would be a Box) and the Matrix which translates into colors.
I suggest you involve your son in doing some personality research. This will help both you and he understand why he makes the choices he does AND will help him learn how to interact with other personality types.
Good luck!
C.