And surely his own ill-judged analysis is evidence of why the performance tables, crude though they are at present, are potentially so valuable. They provide information against which each institution can compare itself, and a benchmark for every institution to measure its own future progress, its own current performance.

The emergence of tables of improving schools (as seen in The TES and The Times) and the rolling average scores seen in the Welsh tables are the most exciting developments this year. We should be lobbying hard not for the abandonment of performance tables (which no political party once in power would countenance) but for their further refinement, so that they can act as one measure of school improvement.

It really will not do for Mr Conway to fiddle with the figures of other institutions in the way he has done. Has he not seen the Secondary Heads Association Code of Practice on dealing with other schools’ exam results?

What I particularly object to, having seen it done all too often, is the way that crude assumptions are made about the precise abilities of an A-level intake in a named institution.

Has he seen the actual GCSE results achieved by students at the two schools concerned? Has he their permission to publish such information? If his knowledge is only based on the performance tables of 1993 and 1995, then his school of analysis is an impressionist one.

There are at least two other disturbing aspects to this article. First, there is the implicit assumption that one sort of post-16 provision is superior to others. “You may have been bamboozled by raw data into believing it’s them, so I’ll supply my doctored data and you’ll realise it is us after all” is the message. We are led to downplay or even dismiss the high achievements of selective institutions.

This is all too easy to assert, but there is hard evidence available to refute it. Mr Conway should read the Department for Education and Employment Statistical Bulletin 495, which compares students’ A-level performances in 1994 with those same candidates’ GCSE performance in 1992. This is a large- scale study which has not received the attention it deserves, though it has been given to Office for Standards in Education inspectors.

It might be thought by some that students in selective schools, who generally do very well at GCSE, would add less value at A-level than those in other institutions. But this is not the case. Actually, it is the other way round. There is a tendency for candidates with any given level of GCSE performance to achieve better results at A-level in selective schools.

The second dispiriting area of the article is its tendency to pit school against school. It may well be argued that this is what politicians want us to do, but that is a poor defence for such action within the profession. It is no defence for anyone who has failed the students. Similarly, it is patronising to those countless institutions which are doing very well for their students, including no doubt Mr Conway’s own, to suggest that only the brightest students are to be highly valued and to contort figures to make yourself top of the league.

Instead, we should encourage the use of the tables as a focus for raising standards within the individual institution and for developing students further, whatever their level of previous achievement. That message, which values all students, would be better conveyed by putting the emphasis on school improvement rather than by condemning one hierarchy only to replace it with another, with yourself at its pinnacle.

Next year, I hope that the tone of commentary on the tables will be more concerned to celebrate the improvements on previous performance made by individual institutions, and that it will seek to encourage the provision of more sophisticated information which will enable this to take place. This seems much more preferable to allowing the manipulation of data to undermine the achievements of other schools.

Roger Hale is head designate of Caistor Grammar School, Lincolnshire