Supporters of the comprehensive ideal have always marched to three slightly different tunes. For some - mainly in the suburbs, market towns and countryside - the motive has been the social desirability of all youngsters, whatever their background, in a local and settled community attending the same school. For others - especially in urban areas - the ideal can be realised only if schools have the full range of ability as measured by standardised intelligence tests taken at the age of 11.

A third radical and far-sighted group have always gone further. They reject the very idea of fixed or predictable ability. The true test of a school’s comprehensive credentials is whether they believe that all their pupils can succeed - and organise themselves accordingly. As Brian Simon, the father of the comprehensive movement, put it: “If the new schools were to be rigidly streamed and the children divided into a set of hierarchical teaching groups, the whole purpose of making the change to comprehensive education might be subverted.”

In short there should be no limit to pupils’ learning - still less a predictable ceiling.

Very few schools, rural or urban, have lived this comprehensive ideal. More likely, schools have reconciled themselves to the inevitability of comprehensive success or failure according to the pupils’ background and their scores on cognitive ability tests taken on entry. Worse still, in large cities, many headteachers believe the route to school improvement is by attracting a better class of pupils. Is this why Sir Cyril Taylor, chairman of the Specialist Schools’ Trust, (TES, August 6) wants specialist schools to control their own admissions? How can schools controlling their own admissions be squared with increasing parental choice, the holy grail of politicians whether from the right or the left?

You may well ask how anyone in such circumstances, which of course includes league tables and published Office for Standards in Education reports, can be sanguine about the realisation of any of the versions of the comprehensive ideal. But there are three reasons for hope, based on a mix of realism and optimism.

First, the introduction of targets for pupils’ learning outcomes has stimulated schools to rediscover “formative assessment”, which became lost in the late 1980s under the blanket anonymity and restrictions of the national curriculum. It is now born again under the phrase “assessment for learning”. Targets encourage teacher and pupil to discuss the process of learning and the next stage of the pupil’s journey. Present improvements in achievement reflect the combination of the individual’s effort to overcome the precise obstacles to their learning and to increase their ability and their teacher’s skills and expertise in helping them do that. Such teachers believe in the ability to transform rather than merely the ability of their pupils. And the best headteachers have the confidence to build belief that all their pupils can enjoy success. There is now a rapidly growing number of such heads and teachers - especially, thank goodness, in schools at the wrong end of the pecking order, in the large conurbations where the systemic obstacles to a fair share of pupils and therefore a more readily established “achievement culture”, is so great. This development in assessment practice and school attitude, alongside an increased knowledge of the best methods of learning and teaching (aided by new technology), represent the greatest cause of optimism for the realisation of the ideals of the comprehensive movement.

The two other reasons for hope are conditional on further change in systemic processes - funding reform and parental choice. But both should be politically attractive.

The promised overhaul of the formulae which determine school funding must include incentives for schools to work with each other and penalties for those preferring to work in competitive isolation. Today’s multi-racial, multi-faith cities require schools to work in partnership if they are to meet all the needs of all their pupils. Working alone they cannot.

Finally, some say the urban comprehensive ideal cannot be achieved without restricting parental choice. But how about increasing it? Consider how parents apply to various schools, albeit within a co-ordinated application system as now. But why not also give them a second, parallel chance - to apply for a nominated “state scholar’s place”? This could be achieved simply by requiring every maintained school to reserve 15 per cent of its places for state-nominated scholars. If a school is over-subscribed, these places would be filled by first giving priority to pupils neither of whose parents have enjoyed higher education.

Such a scheme, with the right funding incentives, would enable the ideals of the pioneers of comprehensive education to flourish as never before.

Tim Brighouse is the commissioner for London schools and Harry Brighouse’s father