The statisticians look at the scores of children the same age. Then compare the results to others of different ages to see if there’s any statistical differences between children of different ages. If there is a statistical difference, then the scores are adjusted to bring them back into line. If there’s no difference, then no changes are made. It’s definitely not as straightforward as simply ‘adding marks’. How would anyone know exactly how many marks to add for starters, unless you actually look at the spread of marks.

In this way, they can ensure there is no advantage/disadvantage that is purely down to age.

Remember that a child born on the 1st September is a year older than one born 31st August. At the ages of 11/10, one has been alive for 10% longer than the other. For some areas that won’t make much of a differences, but for say, vocab, that’s 10% longer time that children have been hearing and reading the English language.

I'm sure you have, but it's not a result of the process as you are describing it. scary mum and Tinkers are correct.

When the explanation link says;

"The standardisation process has “awarded” extra marks to the younger child to compensate for their younger age."

I can see where the confusion might arise.

Indeed, but that quote should be taken in context of the whole explanation and the example on question and the inverted commas around the "awarded" suggests it's not a literal description.

At least in Kent, doesn't make much of a difference... it varied by perhaps 1 std score difference for someone aged 10y10m/10y5m (this was for maths).. Also saw this reply from Kent Council:

There is a limit to the detail I can give, because we have an agreement with our test provider (a company which also carries out the national standardisation which is applied to Kent pupils’ results) that we will not share information which is regarded as commercially sensitive, and this extends to the standardisation process. If “ball park” information will help, though, the standardised score for each birth month puts the raw score in context with the performance of children the same age. If – as is often the case – older children slightly outperform younger ones when the test is trialled, the standardisation will reflect that, in that a slightly lower number of correct answers will yield a slightly higher standardised score for a younger child. The less the effect in trialling, the less the adjustment. The effect of standardisation is generally that a child at the August end of the range will get a slightly higher standardised score than a child at the September end, even if they got the same number of right answers. Usually the greatest range across the year group in an 11+ paper is 6 points, but with the tests we are using at present it is typically less than that.

I think the difference in Essex was much more marked this year. There were several people on that forum complaining about how "they'd got it wrong" and had "gone too far", completely misunderstanding the way standardisation works.