A percentage on its own does not tell you how well a child has done. 70% on a hard paper can be a better result than 85% on an easy one, and a ten-year-old who has just turned eleven has had almost a year more to learn than a classmate born the next summer. A standardised score takes both of those out, so that results from different tests, and different children, can be compared fairly.
It is the number you will see on school assessments, on 11+ results and on most reports that say how a child is doing compared with children of the same age.
How a standardised score works
Standardised scores are put on a fixed scale, so the number always means the same thing:
- 100 is the average. An average child of any age scores 100 on any test.
- 15 points is one step. About two children in three score between 85 and 115, and about nineteen in twenty score between 70 and 130.
- Most scales run from about 70 to 140. Some run a little wider, to 60 or 145.
The number tells you where a child stands compared with others of the same age:
| Standardised score | Roughly, out of every 100 children of that age… |
|---|---|
| 70 | 2 score lower |
| 85 | 16 score lower |
| 100 | 50 score lower, 50 score higher |
| 115 | 84 score lower |
| 130 | 98 score lower |
How is it worked out?
- Step 1 — marks are added up. The child's raw score is the number of questions they got right (or the percentage).
- Step 2 — it is compared with a large sample. The test is first given to a large number of children, chosen to represent the whole country, so we know how the marks spread out.
- Step 3 — age is allowed for. Children are compared with others of the same age, usually in months, so a summer-born child is not marked down for being younger.
- Step 4 — the result is put on the scale. A raw score that is exactly average for the child's age becomes 100, and every other score is placed above or below it according to how far it sits from the average.
That is why two different tests, a hard one and an easy one, can give the same standardised score for the same child, even though the percentages are quite different.
Why not just use percentages?
- Papers are not equally hard. A percentage cannot tell you whether a paper was generous or tough. A standardised score is based on how many children found the same questions easy or hard.
- Ages differ. Children in the same school year can be almost twelve months apart. A standardised score compares like with like.
- Different tests can be compared. Maths, English and reasoning papers are marked out of different totals. On the same scale you can set them side by side and see where a child is strongest.
What is a "good" standardised score?
There is no single answer, because it depends on what the score is for.
- Around 100 is average for the age.
- Above 110 is above average.
- 120 and over is a strong result, and is in the top ten per cent or so of children.
For the 11+, the number that matters is the pass mark for the particular area and year. Some areas set a fixed standardised score as the pass mark; others rank the children and offer places in rank order. Your local council or the school's admissions pages will tell you which applies, and the pass mark is often only announced after the exam has been taken.
What a standardised score does not tell you
- It is a snapshot, not a verdict. Scores move from one day to the next. A child who scores 112 one week might score 106 or 118 the next, on a similar test. One result, good or bad, should not be over-read. A run of results shows far more than a single one.
- It does not measure everything. It reflects how a child did on one test, on one day, in one subject. It says nothing about effort, curiosity or how much a child has improved.
- A change of a few points is usually noise. A move of three or four points is within the normal ups and downs of any test. A steady move over several tests is worth taking notice of.
- It is only as good as the tests behind it. Scores from a well-designed test given to a large and representative group are trustworthy. Scores from a tiny sample are rough guides.
Standardised scores and the 11+
Standardised scores are how most 11+ tests report results, so mock exams and practice tests that give a standardised score are far more useful than a bare percentage. SalisburyElevenPlus.com explains how it works out the standardised scores it gives to families on its mock exams, and what they tell you about the real 11+.