Friend of mine in UK's daughter has been to one school for Reception, another for Years 1 & 2 and is about to go to her third school for Year 3. All private schools, and according to friend, there is always some problem with them - teacher in Reception didn't stretch child enough, Year 1 teacher pleasant enough, but child made no progress, Year 2 teacher "useless" and "hadn't heard anything good about Year 3 teacher" so decided to move her DD.
Personally, I think this is a bit excessive and disruptive for the child. Her DD is lovely, but VERY timid and has been in the bottom set for most subjects through school so far. Her mother is v bright and academic and I feel she expects her DD to follow in her footsteps. I know we all want the best for our children, but surely at this age they should be having fun and making friends, not being hoicked out of school and expected to make a new set of friends every year?