And so the fiasco over the grading of this summer's GCSE English exams rolls on. More than 45,000 children are now expected to resit all or part of their tests next month, after the revelation that exam boards raised the boundary between a D and a C without warning in an effort to clamp down on grade inflation.

Teachers, parents and pupils alike have – reasonably enough – cried foul: not only were children unaware that they would be working to a tougher standard, but those who happened to sit their final exams in June rather than January have come out worse than their counterparts through no fault of their own.

But there is another reason for schools' ire. The all-important national league tables are compiled on the basis of the number of students receiving grades from A* to C. By pushing many down to a D, schools' overall performances have been materially affected at a single unexpected stroke. Given the fierce competition for rankings, with a single D grade able to wipe tens of places off their institution's position, it is little wonder that tempers are fraying and headteachers warning that this year's ratings will be invalid.

All of this only confirms, once again, the farce that is national league tables. Their use as the predominant measure of school performance is highly problematic, creating perverse incentives that see, for example, schools over-focusing on a tiny minority of high-D students to coach them over the line, or even some children not entered for exams so as not to drag down the average.

Such target-chasing is inevitable under the current system; it also stands in absolute contradiction to the core purpose of a school: to educate all to the best of their ability. Nor are league tables the only way to judge success. Far from it. Of course exam grades matter. But a one-size-fits-all national ranking, with an arbitrary cut-off at a grade C, achieves little but the confirmation that schools in better areas tend to produce better academic results.

The Education Secretary is reviewing the situation, and not a moment too soon. It can only be hoped that, by rendering the latest league tables worthless, the mess over this year's English GCSEs will hurry the process along.