Cathy,
Like JBdad, I could have written exactly the same thing about DS6. To the T! Just to remind you, DS is also in 2nd after a 1st grade skip. And, yup, kill and drill single digit addition for us too. He gets all the spelling words correct on the first try. Like your DS, mine also seems fine with everything. The good news is the teacher adores him and she does emphasize lots of creative writing, which can always be challenging. Apparently, he participates actively in class discussions. But he is nowhere near to working to his capabilities, especially in math. He is conceptually beyond arithmetic and the teacher is pretty adamant that he is sufficiently challenged overall and doesn't want to do any more. The fact that this teacher likes DS so much makes it harder to advocate - I really want her to keep a positive feeling towards DH and if I push, he may end up with some differentiation but will it be at the expense of the relationship with the teacher, KWIM?
I'm starting to entertain the idea of afterschooling maybe once/week...but I have mixed feelings about it. I'm not really seeing any "red flags" that he's bored out of his mind and he does tend to challenge himself in his free time.