Very confused wrote:
Thanks - I'm interested in Watford Boys & Parmiters.
The standardization is done by NFER; there are some illustrations on their web site. For the SW Herts consortium, it's based on the 2300-odd children who do the test in a particular year, and the results are not released. Essentially they scale the actual marks obtained by the November-born children taking the test in that year so that they have an average of 100 and a standard deviation of 15, and similarly for each other month. There is a logic to it, but since no data is released it's hard to give numerical answers.
You also need to know that the standard will likely be higher this year, as these schools have been forced to lower the proportion accepted via the test from 35% to 25%.