My DS is in K but is spending about a third of his day in a first-grade classroom. We made the change in early December. He had a bit of a rough start, but things are going smoothly now. In contrast to what others have said, this was very easy to do, but it is not an actual skip but a subject acceleration of sorts. Our biggest issues were 1) a few social bumps (this was addressed by giving him a "buddy" and making sure he knew that the teacher should hear about it if anyone was unkind) and 2) a little bit of distress in his part at the increase in writing expectations and "boring" phonics work. The teacher has helped him not have to do the phonics stuff and he has adjusted to the writing demands.
