Sorry OP & other posters:
I fear I picked up the term 'average' from the Mumsnet learning page " The number of sublevels an 'average' child might make is..." and their grid at bottom of page - link here: www.mumsnet.com/learning/assessment/progress-through-national-curriculum-levels
As usual language and meaning are at the root of this interesting and sometimes heated discussion.
I think Mumsnet learning (but maybe someone from Pearson can come on about this) mean 'typical' - and I wasn't specifically thinking through anything statistically myself.
I suspect that this is about the 'median' on the Bell Curve. An example with IQ is discussed on this QUB website: meds.queensu.ca/courses/assets/modules/types-of-data/symmetrical_and_asymmetrical_data.html
So what they're talking about is the 50th percentile child at the peak of the Bell curve (persuming normal distribution = symmetrical curve) - and that has been taken to be the notional 'average' (meaning here typical) pupil. And from the point of view of explaining expectation that's statistically reasonable - so I'm presuming 4a (from Pearson) would represent the peak of the curve with approximately 48%-49% doing slightly worse and 48%-49% doing slightly better.
I don't know - but someone out there may know whether KS1 and KS2 SATs results are distrubted normally (symmetrically) or not.
-----
Now teachers please do correct me if I'm getting this wrong or have wild notions but:
- 2 sub-levels a year progress tends to work as a rule of thumb from my experience. Typically no sublevels reported in YR because EYFS scoring, and therefore Year 1 you get first NC Levels & sub-levels (if reported to you by your school). These usually are in the NC Level 1 range for most children.
From there on it seems to make sense with levels working c to b to a then up to next main level (e.g. 1c - 1b - 1a then 2c, etc...) then at the end of each year progress would look like:
YR 1 - let's say a 1c/1b
YR 2 - let's say a 2c (2 sub-levels & level 2 for SATs)
YR 3 - 2a
YR 4 - 3b
YR 5 - 4c
YR 6 - 4a
-
The general expectation is for schools to get the vast majority of pupils to Level 4 or better.
-
The tracking of 2 sub-levels a year is about tracking progress (at least for me). If there is good communication between teachers and myself, I'm able to understand that DDs are improving and mastering what they're taught or if they aren't progressing through an early warning that they're struggling/ stalling in some areas.
It's useful for me at home, where I do a lot to support my DDs, and hopefully also useful to track at school. (I can't speak for all schools, but our school does track 2 sub-levels progress per year for all pupils in KS2).
HTH