L.F.
Dear T.:
I'm just going to throw in what I've seen, with the upfront I didn't have this issue. My daughter went to kindergarten where she continued on in grade school.
I saw several children who went to a local daycare that offered kindergarten then come join us in the first grade. Every one of them was a little lost. They didn't know this school's routines, they didn't know where anything was and they all were little fishes out of water for the first month. Also, the kids who were there in kindergarten knew each other from the last year.
My two cents is switch sooner rather than later. It's nice to start the harder academics, kindergarten, first grade, in a place you already know and some friends you've already made.
L. F., mom of a 14-year-old-daughter