We are skipping K for DS5 and sending him to 1st this fall. So, obviously no experience with it yet, but I can keep you posted as we go through the year if you'd like. DS has a Feb bday which puts him generally in the middle of his current class age-wise, so he'll likely only be about 6 months younger than the youngest students.
We're not worried too much about the school "transition" because he was in a preK+Spanish immersion program at the same school that was a full day. He's familiar with the school and how it works, and their K is more similar to the preK (they actually swapped rooms with the K class after lunch, so it was all the same materials for both classes) than to 1st, so it would be a transition anyway. He did very well with the full day as a 4-year-old, but this is a kid who hasn't had a nap since about 18 mo. and for whom energy is not a problem.
