We told DS it was a possibility (he was 6 at the time) and he toured the new school once, then stayed for a half day another time (in the classroom he was going to be in there). He loved both visits, which helped. We did get a lot of questions from parents about whether DS was coming back to the original school (we were vague, saying we were still considering our options, etc.).
That it had been a really rotten school year probably eased the transition for DS. He was a little concerned, but overall fine with the whole thing.
