Percentages are a misleading way of calculating any organisation's performance year by year.

And nowhere are they more inexact than in school examination league tables, which take no account of difficulties faced by individual schools. Or of social problems, and advantages, prevailing in the areas which some of Britain's schools serve.

However, though it is worrying that Swindon is performing well below the national average, we believe parents should not be depressed by the comparatively small statistical slide in this year's figures.

A school in a supportive community which has an exceptionally large share of very bright children is clearly at an advantage over one which has to battle against social problems and parental apathy.

But that doesn't mean the school from the problem area is failing.

The sooner the value added system of assessments are introduced, the better school league tables will be.