Standardised scores

[Bitlost]

Dd’s teacher (year 5) tells me that DD’s standardised score in maths is 115, which is the highest. I thought the highest was 120??? Confused. Am I missing something?

yes it does go higher,. maybe she was the highest in the cohort at her school., does it really matter?

Probably doesn’t. I’m just trying to understand the system.

Yes it does go higher. Your dc scored exactly within 1 standard deviation of the mean (average score =100). Basically means your child scored above average.

She meant the highest in her cohort at that school.

Generally speaking, 100 is the exact average, anything from 80-120 is within the average range, anything below 80 may indicate some learning support is needed and anything over 120 is really good.

I think KS2 Sats go up to 120 but other test like nfer used in other year groups would go up to even higher scores.

Scaled scores are not standardised scores - they are completely different things.

Standardised scores are reported for many standard tests of ability and attainment (WISC, Stanford-Binet, BAS, WIAT etc). They are constructed to be normal, usually with a mean of 100 and a standard deviation of 15. If you know the standardised score, you know exactly where in the distribution you are (the percentile). Most standardised scores will cover the range 60-140 or even 40-160 (4 standard deviations).

Scaled scores (as used for SATs) appear at first sight to be similar, but are fundamentally different. They are contrived such that 100 = the "expected standard" (NOT the mean). The distribution of scaled scores is generally not normal, and usually not even reported. You can't work out the percentiles from the scaled scores. A score of 115 does NOT indicate you are 1 standard deviation from the mean. Scaled scores generally cover a far smaller numerical range than standardised scores (e.g. 80 - 120).

Since the underlying distribution is unspecified, the score range highly restricted and the percentile equivalents indeterminate, scaled scores are useless for practical purposes such as gifted identification.

If one were cynically inclined one could speculate that one reason for introducing scaled scores was to fiddle the numbers so that no child could ever be identified as gifted by the test, and thus no action would be required or demanded, providing no one digs too deeply into how the numbers were generated.

extra, great explanation. Thank you.