It's weird to talk about one's kid, but even worse to write about oneself. Nonetheless (deep breath), here goes. I was that kind of kid -- well behaved, attentive, loved by my teachers, accelerated a couple of grade levels in English and Math. Things started going downhill in 5th grade and became loathsome in 7th-8th grade -- due to, I think, a combination of growing boredom and peer issues. Ninth and 10th grade were good peer-wise, but by then I had gained an unhealthy disrespect for school. After 10th grade, I went straight to college, which on the one hand, saved my sanity, but on the other hand, I somewhat fumbled because I had no study habits to speak of (work habits, yes; I was used to handling large amounts of work; but being challenged was something completely new to me). I'll stop with the story of my life there (I turned out fine, by the way; we're a resilient group, I think, but would have had an easier time if my needs had been addressed). My point is: Yes, your kid is gifted; I'm so glad for you that everything is going fine, but be alert (without being paranoid!) to warnings that things have changed, because (if) once they do, you might want to look into the cause and think about an intervention.
I wish you and your ds all the best.