Where to find information about Standardises Scores

[StandardisedScoreConfusion]

My child has a standardised score of 125 in Writing which is 28months above their cronological age and a standardised score of 123 in maths which is 4 months above their chronological age. Can anyone explain why 2 points make such a difference in the chronologiacl age? Does anyone know how good these scores are? (Is this in the best 10%?).

It would probably be useful if you mention which type of test. SATS only go up to 120 so it's not that.
Potentially a misprint and the 28 months should only be an 8 bringing it more inline with the other score

My child says it is the RS assessment from Hodder. I found their website but still cannot find anyting about the mark distribution and how they come to the insight how many months ahead a child is.

In my experience different “standardised” tests vary hugely. It might be worth looking at what the maximum mark in on this particular test. I know “broadly average” is generally about 90 - 110, so 125 is high, but whether very high or just high I can’t be sure.

I looked at their scale and 123 is 92 percentile and 125 is 94 percentile. Assuming both Writing and Maths use 100 as the average, it can only explained by this percentile difference. They explain it on their website.

It's high by selective school standards, but not 'very high'.

If you want a breakdown of your child's strengths and weaknesses you might want to look into getting a WISC-V assessment. This is particularly useful to pick up relative weaknesses in academically strong children such as processing speed and working memory.

The 4 months above chronological age is probably a typo. A standard score of 123 would be significantly further above chronological age.
These test scores are normally constructed to have mean/median = 100 and standard deviation 15. So both the 123 and 125 are in the ballpark of 1.5 standard deviations above the mean.
The tests are only accurate to within 5-7 points so there's no real difference between 123 and 125.
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The short answer is yes, your child scored in the top 15% (RS goes up to just over 130 on a standardised score). However, you should bear in mind that 100 on these tests is not the govt expectation but the average score by the pupils who sat these particular tests (it’s a smaller pool than everyone of that age, obviously, and a lot of selective schools don’t do them).

Thank you! I finally found their scale.