Centile

Centiles compare your child with 100 children of the same age. A child on the 9th centile scored higher than about 9 of those 100 children, and lower than about 91 of them. The 50th centile is the middle of the range, not a half-marks score.

You will have met centiles already in your child's red book: the NHS explains that the curved centile lines on its growth charts show the average Descriptive range The words a report uses to sum up a score, like 'average' or 'extremely low'. Tests draw these bands in their own places, so the same word can mean different scores. Read the full definition of Descriptive range weight and height gain for babies of different ages. Assessment reports use the same idea for test scores, usually under the name percentile. Centile and percentile mean the same thing.

The most common mix-up is reading a centile as a mark out of 100. The 9th centile does not mean your child got 9 percent of the questions right. It is a position in the queue, not a score.

One more thing worth knowing: centiles bunch up around the middle. Near the 50th centile, a tiny change in the raw score can move a child many centile places, so a swing between two reports is not necessarily a real change in your child.