I agree with La Texican - I would really look into unschooling. He seems like a great candidate for it. He is totally going to be on his own path in life.
Interesting to hear you mention that he has no desire to show off his intelligence. I'm beginning to wonder if my son (17 months old) is color blind - lol - just because ignores me when I ask him to get the red item. But several months ago he pointed at my cranberry juice in a cup and said "red," so I'm sure he's just fine.
He's like that with everything. Who knows what he's picked up that we don't know about yet. Though I doubt he'll be picking up Russian at any point.
Your little guy is very special. Don't let the schools try to "fix" him.
