There is not a set number of points for being a certain age. "Standardised Scores" take account of age by only comparing children with those born in the same birth month. Generally it has been found that children born in the beginning of the school year score higher marks on average than children born at the end (not surprising really). However, how many less correct answers an August child needs will vary from year to year and from exam to exam depending on how all the other children in that particular cohort perform. Here is the link to the explanation of standardised scoring on this site - it also has a link to NfER's page with a more detailed explanation:
http://www.elevenplusexams.co.uk/standa ... scores.php
Hope this helps.