A while ago I started a threat about seeing one of may DS's Y2 maths lessons and getting the impression that it was too easy for him (he was with mainly Y1s and seemed to do the tasks 3x over). DS never complained, he likes easy, and it gives him lots of time to dream and chat - that is DS's problem and it did keep him behind, but we worked on his maths at home since the summer and he did improve.
Repeatedly, I spoke to his class teacher (his maths teacher was not available to talk to me!), and she assured me that Miss X will differentiate appropriately for DS. I spoke to the Deputy Head and asked for his levels, and she told me that the school does not give that information to parents, but assured me that he is in the right place and that I wouldn't want him to struggle (I felt patronised!).
The class teacher suggested that she will tell me what she does with the Y2s and I can then practice with DS. I saw her last week and appeared a bit surprised as I thought DS can already do what she was going to do with Y2. She finally assessed him and told me (a bit embarrassed) that he did as well as the best children in her Y2 class and that he will be with the Y2s now. 
Now I am thinking, what has gone wrong? Why were expectations so low? It was surely my DS's attitude, but is he the only 6yo who sits there dreaming about Starwars, lego and has a tendency to be silly? Next year in junior school he would have been in the bottom set for maths, now he is more likely to be in the top set.
I get the impression maths didn't click with him aged 4 in YR, but now aged almost 7 he seems to be quite able. Is it in YR where teachers form an opinion of a child and set expectations accordingly? Don't they grow up a lot in those first years at school.