Expected progress is that a level 5 would 'gain' three levels and get a B - all this is now out of date of course! [no levels at KS2 although they will be used in these tables until the current cohort works through to GCSE}
Most school aim for 'more than expected progress' ie at least a grade A for level 5s.
We get matrices of KS2 levels against GCSE grades and this is part of the data Ofsted scrutinise. You can see the National picture if you google "KS2 to GCSE transition matrix" and select 2015.
Wow thanks a lot, I can now have some fun with stats and excel!
Puts much more meaning into what levels and grades mean by turning them to percentiles.