Mine have always settled really easily into new schools, although up here in primary they only move class once because the classes are mixed, P1-P4 in one class room and P5-P7 in another and the school in so small that they all know and play together anyway. I think when they first started in P1 they had a buddy for the first few weeks which was someone from the bigger class who looked after them at play times.
However when they have had to move school we have just told them it is an exciting new adventure because they get make loads more friends and meet new people which they all love to do anyway