The link above has the data for 2015, lots of breakdown of the overall stats, including average mark split into term of birth, sex etc. I expect there must be a lot of variation still between individual markers, and also how much effort you really make as a teacher / ta collecting the evidence to confirm someone is exceeding, rather than teaching the kid, or helping someone else out who's not there yet. Unfortunately the data available on line doesn't really provide info to see if there are different spreads, (they may have more data available if you're really interested in studying it of course) The council data is interesting, Lewisham for example gets much higher than average to get at least expected in all seventeen areas, yet their average mark is not out of line, suggesting less exceeding of course, so there is national variation I'm sure.
Things you clearly from the data (this is 2015, not this years) Summer born's get around 4 less than Autumn. (giving 3 points for exceeding, 2 for expected, 1 for emerging) So age is quite a difference. Male / female also.
DD's school used some evidence that the parents had been sending in "wow stickers" as part of the judgement, so I also think how the parents engaged with the school and how the children reacted to that scheme would've made a big difference to what could be given.
Ginmummy1 Moving and handling does seem odd, DD can ride a bike comfortable, swim lengths, climb a rope, monkey bars or anything in a playground, can tie knots, screwdrivers, knife fork, scissors etc. It's one of her strongest areas of the 17 I would've said, yet it was one of only a few that she didn't get exceeding.