THE publication of school league tables based on exam results divides opinion.

Critics argue they are misleading because they focus on one measure and do not inform parents about the wider context of a school or how much it helps pupils improve. When the subsequent tables are published they can be used as a shorthand by parents for whether a school is “good” or not when that is not what they tell us.

However, there are strong counter-voices, with the UK Statistics Agency criticising the Scottish Government a few years ago for its strategy of publishing school results individually without making comparisons.

In fact, the government and schools quango Education Scotland work hard to try to prevent easy comparisons, publishing exam data on a school by school basis on the Parentzone website. That means parents wishing to make a comparison between two or more schools have to view information for each school separately.

Our tables allow for a more direct comparison, but there are a number of important caveats.

Our benchmark of the proportion of pupils achieving five or more Highers by the time they leave school appears a good one to judge performance. However, it does not tell us whether those results were achieved in fifth or sixth year, so favours schools where more pupils stay on until S6. The measure also takes no account of how many pupils are in a particular year group – meaning small schools can yo-yo up and down the league tables from year to year.

The major issue with school league tables, which is almost impossible to address, is that it does not take any account of the social mix of a school.

Because deprivation has such a significant impact on exam performance, tables tend to artificially promote schools in middle-class areas at the expense of those serving more disadvantaged communities.

This is not necessarily anything to do with the quality of the school, but simply because schools in leafy suburbs have a higher proportion of pupils from richer backgrounds who tend to perform better in exams.

It should be remembered the figures are not worked out as a proportion of those who sat Highers, but as a percentage of the S4 roll, meaning even pupils who did not sit Highers are counted.To give greater context to the data, the Scottish Government publishes a “virtual comparator” benchmark which is supposed to show how a school should be performing – although these benchmarks have been criticised for their accuracy. The government also publishes the proportion of pupils from the poorest neighbourhoods at a particular school, giving even greater context.