THE publication of school league tables based on exam performance is always controversial because the information can be misleading.

On the face of it, The Herald’s benchmark of the proportion of pupils achieving five or more Highers by the time they leave appears a good one to judge a school’s academic performance.

However, it does not tell us whether those results were achieved in fifth or sixth year so it favours schools where more pupils stay on until S6 to accrue more qualifications.

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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 depending on how academically-minded their pupils are from year to year.

More generally, critics of league tables argue they are misleading because they focus only on one measure and do not inform parents about the wider context of the school or how much it helps pupils improve.

There are strong counter voices, with the UK Statistics Agency criticising the Scottish Government in 2013 for its strategy of publishing school results without making comparisons between them to avoid league tables.

While still making it hard to construct league tables by not publishing exam results on a national basis, the Scottish Government introduced new measures last year that give greater context to the data, including a “virtual comparator” benchmark.

That shows how the school should be performing given the socio-economic background of its pupils and can help parents decide whether it is punching above its weight or coasting.

In addition, The Herald has chosen to highlight only those schools at the upper end of the scale rather than featuring those that have lower proportions of pupils passing exams.

As a result, the table should be seen as a celebration of pupil success rather than a vilification of schools who have not achieved so highly.

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, the tables tend to artificially promote middle class schools at the expense of those serving poorer areas.

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This is nothing to do with the quality of the school, but simply because schools in leafy suburbs have a higher proportion of pupils from richer backgrounds and therefore their statistics look better.

It should be remembered that 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.

The tables also give the impression that “academic” schools are good school, when they might not be so effective as serving the needs of all pupils, such as those best suited to a more vocational route.

Ultimately, parents should not use league tables as a basis of where to send their children. What they really need to know is whether pupils can achieve their full potential wherever they go.