This has been super interesting to read. I don't know if DS is gifted. I"m not even sure how to measure that to be honest and I don't think our school has either testing or gifted classes so I'm not sure there would be any point. I do know DS is going into 2nd grade and reading way above grade level. He can read Harry Potter easily and could probably read articles in the Economist though he comes back with a million questions about concepts he doesn't understand ("Mom, what's inflation?"). He's above grade level in math though I'm not sure how high. He was bored silly last year. His class had only 18 kids, btw, but an uninspired teacher and little differentiation.
We are trying in him normal 2nd grade this year but we've talked to the principal about getting a more appropriate teacher. We're also going to be a lot more pro-active about being sure he's getting appropriate work. I'd consider skipping him, but I don't know what anyone else thinks of that idea, including either DS or DH. He's already the youngest in his grade.
Anyway, the concrete ideas here are super helpful. I might try that Cool New Words idea and see what he thinks. I don't want another year of sheer boredom. That's not what school is supposed to be about.