In years 3 and 4, children are expected to make 3 sub-levels' progress (one whole level). This means that, in either year 3 or 4, a child should make only one sub-level. Usually this ends up being year 3 due to the change of curriculum, expectations etc.
Saying that, in my school we assess year 2 differently. In maths, for example, the children are assessed on all aspects: calculating, shape, data handling etc. In year 3, we only teacher assess on calculating and problem solving. This massively skewers our results because some children are fantastic at shape but awful at number, and vice versa.
There are children in year 2 at the moment who are 3a writers, apparently. I was a bit
at that. Seems exceptionally high. That teacher has decided to use a different mark scheme too, so...
Like others have said, has your DC made no actual process, or is it just sub-levels you're referring to?