After four years of GCSE league tables, the most depressing observation is not the widening gulf between apparent achievers and non-achievers but the insidiously growing acceptance that the academic standards of schools or education authorities can be determined from the percentage gaining five or more A-C grades.
We know that only the most able 45 per cent of a normally distributed cohort can be expected to hit the five A-C target.
Of course schools can make a difference and there are effective and ineffective schools, but quite small differences in the overall ability distribution of year cohorts may have a disproportionately large effect on the numbers of pupils in the potential five A-C group. For this reason quite large differences in the five A-C percentage can result from no changes at all in the effectiveness of teaching and learning.
For schools which already have substantially skewed intakes and small numbers of able pupils, any such variations will be even greater, swamping any modest incremental improvements which follow from genuine increases in school effectiveness.
This would make valid investigation of school improvement difficult enough, but the league tables themselves affect the ability distribution of intake cohorts, so it is not possible to separate real progress in teaching and learning from the huge benefits in A-C outcomes which accrue from "moving upmarket".
In many urban neighbourhood schools, however, even this route to apparent success doesn't work, because the first fruits of success are increased patronage by the most socially deprived families which live nearest.
If the school is really popular, despite the misinformation in the league tables, then the result may be ever greater social and academic polarisation, because middle-class children from further afield won't be able to get in.
Anyone using these arguments now risks being dismissed as a "social determinist". The current fashion is to believe that "high expectations" inevitably lead to miraculous academic attainment.
Both Gillian Shephard and David Blunkett would have us believe that the polarisation in performance (TES, December 15) must reflect a growing epidemic of low expectations across huge areas of the country, which prevails despite the "driving up of standards by market forces" (to which principle both major political parties now seem equally wedded).
Individual children are not limited either by junior school test scores or social class, and real, genuine, comprehensive progress across all abilities and income groups can be made, but not until the market model is abandoned.
Only then will we be able to concentrate our energies on maximising effective learning supported by a system of fair funding, in which an artificially created market is not allowed to distort and destroy the absolute right of every child to high quality education alongside their peers in their neighbourhood school.
Headteacher The Alfred Barrow School Barrow-in-Furness Cumbria