My friend asked her school last academic year whether she could swap from Year 5, where she had been for 6 years, to Year 1, as the whole staff were asked if they would like to move year groups. She did this as she felt she was lacking in KS1 experience and wanted to experience a new challenge.
All good, SMT agreed, and she started in new year group in September.
Some parents have been in to ask the HT if she was "moved" because she couldn't cope with KS2!
When I was a class based teacher, I did the same and asked to move year groups/key stages a few times for CPD purposes, and also had comments similar to the above made by parents.
Why would moving year groups or roles be seen as some kind of issue? I don't get it.