"If he didn't know I was watching he would get 100% every time." There is
the essence of your problem, the collision between intellect and affect.
Depending on how you and your school authorities handle this (and also how
other children treat your child) you can wind up with either a 16 year-old
university graduate or a self-destructive Youth Authority inmate.
You are on the right track by noting how he reacts to perceived pressure
from you. All you can do at this point is make options available to him
without being perceived to be "pushing" anything. Here are some things to
try: get a chess set with instructions or a basic introductory book, set
it up somewhere and let him choose--or not--to explore it. Similarly,
acquire a Jr. high or high school chemistry or math book and leave it
where he can choose to look at it. (Often such books are available from
free as discards from public school districts--don't worry if the books
aren't brand new.) See if your local PBS affiliate shows "The Mechanical
Universe" video series.
Do some web-searching for "Asperger's syndrome" and see if the
symptoms remind you of anything you've seen. The experts won't say it this
plainly, but it's just "obsessive-compulsive" behavior at a child's level;
this isn't necessarily bad, because what's a Mozart, Bobby Fischer, or
Bill Gates but simply obsessive behavior channeled into a progressive
activity? (A lesson for the ages: Mrs. Gates hired an expert when Bill was
13 and she was worried he spent too much time by himself--the lady PhD
said, "leave Bill alone!")
The best move you could make is to seek out others in your situation.
Just one good friend he can relate to could solve all your problems
without you ever having to resort to expensive (and frequently
ineffective) "professionals". Unfortunately, our universities are loaded
with people who have a tremendous ideological agenda, usually from the
point of view that forced equality is the solution to everything. (Dylan
Klebold was a gifted individual subjected to megadoses of this kind of
social programming.)
You are in a great position to obtain the best outcome for your son
by getting on top of the situation this soon. Should problems arise as he
goes through school, the best solution is always going to be talking to
him in plainly rational, adult terms; NEVER let him feel that he is being
excluded from any decisions. (This is why the juvenile justice system is
such a mess, they treat the kid like he's being dangled on a string.)