When my DS changed schools mid-year, the teacher told the class the day before, which worked out well. DS's classmates had an opportunity to say good-bye, and to give him little notes. One girl gave him a very special and thoughtful little goodbye gift. I think it was good in our situation for the kids to be able to say their goodbyes. I think it will probably depend on your kiddo's personality whether you want to ask the teacher to make a big deal, no deal, or something in between, out of any mid-year skip.
Great idea.
We are working on a mid year skip now. Mr W has visited his new class once and we are talking to him about it. We'll go back right before the break, then talk about it over the two week holiday to include driving by every other day.