I should perhaps add one more point.
There is an anomoly regarding anone who have been allocated a score of 141. To quote from the QCA report:-
Very low and very high age standardised scores are printed in the tables as ***. This means that they would be below 70 or above 140, but cannot be calculated with the necessary degree of statistical reliability. If an exact score is needed, for example, to calculate an average for the class, 69 or 141 should be used for these pupils.
The same applies to 11+ Age Standardisation, so if 2 candidates each scored 141 this doesn't means that they both scored the same, it just means that they scored so highly they were not able to accurately calculate an age standardised score so they just allocated 141 as the highest avalable. So it's perfectly possible in theory that two children of the same age achieving raw scores of say 75/80 or 80/80 respectively could each get a standardised score of 141! Of course this would depend of the degree of difficulty of the particular test.
This was one of the issues with the old Warwickshire 11+ exams where a high percentage of candidates were allocated a score of 141. The reason why there were so many high scores was because test scores were Age Standardised against a National Sample of chilren of average ability rather than the 11+ candidate entry which is normally the case.
There may be something unusual as well with the Bucks Age Standardisation as the average should be 100 but isn't. (See previous discussions on this with Patricia et al - not sure if we ever got to the bottom of this)