Moving isn't usually so easy in primary school, unfortunately.
ds2's Y4 teacher was a miserable bat who sounded to be always grumbling at somebody; once we caught on we were able to make him feel better about it - "it's not your problem, it's hers, just keep your head down and next year you'll have someone else."
He had a great Y5 teacher - then the Y4 teacher switched to Y5/6 so there was a danger of him getting her again in Y6 (and, according to him, a lot of the children were a bit dismayed) so we asked, very specifically, for him not to be put in her class, and he wasn't. Phew!
One of his projects this year has been "A Story About Me" and he really let her have it in that - not sure if his Y6 teacher let her see it...I rather hope he did but I don't know. (When a 10-yr-old writes, in all innocence, that he loved being in R, Y1, Y2, Y3, Y5 and Y6 but that his Y4 teacher was always angry at him, it should make you look at yourself, shouldn't it?)