Scaled scores and standardised scores – what’s the difference?

With so many different assessment measures being used throughout primary schools, we’re often asked to clarify the difference between them. So we’ve gone back to the drawing board to provide some quick facts about two key test outcomes: scaled scores and standardised scores (because while both show performance, they aren’t quite the same thing).

National Test scaled scores

1. The National Tests (or SATs) scaled score threshold of 100 is set in advance and represents what the DfE consider to be the 'expected standard' that each pupil should achieve at the end of Key Stage 1 and Key Stage 2.

2. The raw score (or number of marks) required to achieve a scaled score of 100 in the National Tests is set by the DfE after the National Tests have been taken and is subject to change each year.

Standardised scores

3. Standardised scores should be used alongside teacher judgement, rather than instead of it (after all, you’re the experts on your own class – standardised tests exist to back up what you already know).

4. Standardised scores are based on the performance of a nationally representative sample of at least 1,000 pupils taking a particular test at a particular time, and therefore do not change over time (unlike the raw score required to achieve a scaled score of 100 each year, which is modified by the government).

5. On a standardised scale, a score of 100 represents the exact average achievement within the standardisation sample – but a wider band is usually given to help schools understand a broader representation of the average. This is usually based on what statisticians refer to as ‘standard deviation’ from the mean average.

6. Standardised tests help teachers to benchmark pupil progress and attainment against a national average, and enable teachers to identify strengths and weaknesses across the curriculum to inform teaching.

7. There is no relationship between scaled scores and standardised scores without specific research undertaken by the test publishers. They are entirely different measures. We offer a correlation between the two scores to help teachers to see how performance in our standardised tests is likely to translate into a scaled score in the National Tests.