Thank you so much for a nice welcome and quick response. I will clarify that our peditrician is a young father with kids in our school district (not sure what primary school though). The reason the grade-skipping even came up is because he happens to have a boy much like my own when he entered K a few years back, and they were recommended to grade-skip about 3 months into the school year (not sure by whom, as the teacher felt he was doing fine in K). At the time, I was seeking his advice on whether to enter DS private K last year (as he just missed age cut-off for public). I really have no intention of pushing DS5 ahead. If the learning gap is too a great an issue, I would much rather consider a skip after K. I strongly feel DS5 needs to get the semantics of school under his belt a bit (and also fill in the gaps that he hasn't learned: telling time, phonics, staying in his seat, cafeteria horseplay, etc).
I hear that the school DS will be attending is really great according to my friends whose kids attend (and many of them are teachers). I even had the opportunity to speak with DS' new principal this spring. I felt like I was maybe being too forthcoming with information about DS and his learning, but I decided I really didn't care. She said they often try to pair a the advanced learners together in a few of the classes (there are 5 Kindergarten classes at the new school)as a way to help those students and the teachers both with learning enrichment material.