It sounds like he is learning to blend in at school which may have some social value. If he as bored and frustrated as you think, his behavior is likely to deteriorate. What kind of gifted services and/or acceleration does your school district offer? You may need to contact someone beyond your school building to figure this out. You really need to be the advocate for acceleration or an alternative placement. If the school hasn't gotten back to you, you need to bug them.
Yes, this does happen to other kids. I still remember my DS10 coming home in first grade and announcing that "Math is boring and stupid." The class was working on "making 10" while DS10 was figuring out things like exponential powers. DS10 is now in a gifted classroom and much happier (though still not really challenged). Sadly, even a gifted classroom probably won't be much of an academic challenge for a PG kid.
