I did obtain the Standardisation table for a previous Birmingham CEM 11+ exam some years ago under a FOI request. I posted this on the forum:-
All I can tell you is that in 2006 (which was one of the early Durham CEM tests) - for a child of my son age (10.85 years) at the time of the test the following age standardisation conversions were used:-
63/100=113, 64/100=114, 67/100=116
43/82=113, 44/82=114, 46/82=116
49/70=113, 50/70=114, 52/70=116
The only thing I would point out is that the raw scores are significantly less than the 90% requirements claimed by some parents and also much lowere than typical NFER practice scores.
I recall that the around the area of the pass mark 116 (KECHB was 347 that year) the difference between the raw scores for the oldest and youngest child was about 7-8 marks in each of the sections. viz for VR for example the youngest child might only have had to 62/100 whereas for the oldest it was something like 70/100.
Although this varies from exam to exam, typically the difference in raw score between the youngest and oldest child is about 7-8 raw score marks to achieve the same standardised score. So the difference between a Aug and Sept birth date (ie 1 month) is unlikely to be more than 1 raw score mark for each standardisation(paper in this case)
Hope this helps