Ultra, here's what I think. The worry is at this point unnecessary. You've got this nice, well-adjusted little guy who's way ahead. Do I remember right that he is mostly not miserable at school, and not feeling an intrinsic need to race ahead?
Honestly, our DS10 got no "academic curriculum" that was new to him during his first few years of school, but he was learning and growing in other ways. He did a ton of advanced reading about things he loved outside of school, and a ton of learning how to participate, make friends and be a friend etc. in school. Those early grades are heavy on math and reading, but they are also heavy on play skills, handwriting, and other soft skills that are worth having.
This forum is awesome, but there is a prevailing tendency to feel that the child must be pushed to his/her limit on academics, or there's something wrong. I don't know that that's true in all cases. It is IMO okay to watch the whole picture of what your child is learning, judge whether they're learning in the big picture sense, and decide not to pursue the perfect academic fit for a while.
If a child is becoming depressed and frustrated, or isn't learning (in the big picture sense), then you can push for and make a change. If the K-1 split isn't a good fit, trust that you will notice, and trust yourself to determine better options when they're needed.
DeeDee
