Suddenly, old orthodoxies are suspect, and older ones are reasserting themselves. Having once been the party that led the move away from selective to comprehensive secondary education, Labour is now having second thoughts.

The disenchantment with comprehensives - at least among the political and journalistic middle classes - is a far cry from the Seventies, when Labour cabinet ministers’ children packed the London and Oxfordshire comprehensives.

The then rhetoric of the common school and achievement for all sounds tired. Instead, the once right-wing rhetoric of choice and diversity seems to appeal across the political board.

A generation of politicians who did not experience the implications of selective education is ignoring them. For those whose image of comprehensive schooling is a grey picture of disorderly and mixed-ability underachievement, anything may appear better, even selection.

The fashionable flirtation with selection might soon be over if the educational spotlight fell on Kent, where the 11-plus is still almost universal.

Kent offers a pointed picture of the past: grammar schools, secondary modern ones, the whole Fifties paraphernalia. The county displays - as in some “living history” museum - exactly what the consequences of a return to selection would be. Labour should not contemplate turning back the clock before seeing Kent, and pondering carefully on it.

What does Kent reveal? The county does - as might be expected - have some very successful grammar schools, as any reader of the national league tables will be aware. The more selective of Kent’s selective schools understandably produce exceptional outcomes. But - and this may be the crucial fact - the county as a whole is performing below national average figures at GCSE level. Using the five higher-grade GCSE benchmark, Kent achieves an average of 41.9 per cent, compared with the England average of 43.5 per cent.

A deeper look into the performance tables for the county reveals some depressingly low examination outcomes. Kent “high schools” (non-selective schools in grammar school areas) achieve an average of 20 per cent on this same benchmark. But there are 19 high schools that score between 11 and 20 per cent, and 14 that score between 1 and 10 per cent.

One poignant page of the Department for Education and Employment performance tables shows a boys’ grammar school of some 800 pupils with 99 per cent achieving five or more higher grade GCSEs: alongside it is a mixed secondary modern of some 500 pupils with 3 per cent. Another page shows a 900-pupil secondary modern school with more than half its pupils having special educational needs, with most grammar schools scoring zero on this index.

These dreadful disparities, a consequence of the system, do no one any good. Kent’s few comprehensives (“wide-ability” schools in local parlance) achieve well against national figures, despite a county-wide “creaming” effect.

But the predominant picture is of a sickening see-saw of success, in which one end is perpetually uppermost. The other end is perpetually grounded, dealing with the overwhelming proportion of social and educational problems. It is hard to avoid the conclusion that the selective system, which involves the co-existence of grammar and secondary modern schools, creates in Kent underachievement in the system as a whole and the most inequality of educational opportunity.

Parents and children are the victims. In the west Kent area, for instance, there are over-subscribed church comprehensives, a scramble for the grammar schools, and a cross-border flight to the comparative sanity of comprehensive East Sussex. Choice is apparently on offer, but unless a parent is a churchgoer or has a clever child, there is little.

A further casualty is the integrity of primary education. Heads are required to recommend a child’s suitability for one or other sector of the divided system, and parental panic about the possibility of non-selective education leads to a noxious emphasis on informal entry-to-grammar-school league tables. The fact that Kent spends Pounds 18.5 million annually on bussing children around the county, largely to selective schools, is a further implication of selection.

In some respects Kent offers a dream of diversity and choice which former Education Secretary John Patten himself might be proud of. Are there not schools of every type? Are there not grammar schools, comprehensives, high schools? Are there not local education authority schools, grant-maintained schools, city technology colleges? Are there not co-educational and single-sex schools? Indeed there are, but the divided and disintegrating system only offers choice for some, selection for some, achievement for some.

Inherently, Kent is a nightmare of inequality of opportunity and esteem, a system that cries out for constructive reform. If members of the Labour front bench are really attracted by the rhetoric of choice and diversity, and going soft on selection, they should visit us, soon.

John Caperon is head of Bennett Memorial Diocesan School, Tunbridge Wells, Kent.