I have to say...
I really struggle to understand how Standardisation will affect DD, as she is 10yrs and 4mths will she get more marks than the older children?
She will need to attain fewer raw marks than an older child to reach the same same standardised score. How many fewer marks will vary somewhat from year to year and from test to test as age standardisation depends on the actual differential in the marks scored between children of different ages in the cohort in a particular exam.
Theoretically if the children with August birthdays were scoring the same average as children with September birthdays in a test, then there might be no difference in the scores needed to attain a particular standardised mark - but invariably younger children score less on average, so age standardisation works so as not to disadvantage the younger children.