From the moment I entered educational politics in the 1930s, I became convinced that the ending of the divided post-primary system and the abolition of privilege within it was the crucial step needed to give working-class children their birthright in education. The questions were, how? And what would we put in its place?

The 1944 Education Act provided secondary education according to "age, aptitude and ability". Such innocent and commonsense-sounding words. But they became the foundation of a postwar system every bit as divided and class-biased as in the bad, pre-war days.

It was put over by the con trick of renaming "senior schools" as "modern schools". It was "modern", apparently, to leave school earlier than in the grammar schools, to have larger classes, and to lack specialist teachers, for example in maths, science and modern languages. It was "modern" to spend less on those who needed education most.

What appeared to be final success was achieved by the Wilson government, which decided that rather than set up a compulsory system throughout the country, it would replace the existing divided system by a comprehensive one under the effective control of the LEAs.

Most LEAs responded quickly and, after 1967, comprehensives began to cover the country. Many, however, could not be truly comprehensive because of the continued existence of grammar schools, and because of the difficulty of developing the new schools within existing unsuitable buildings. So the new system was flawed: the money was not made available; hybrid systems continued for years in some LEAs; and many comprehensives were so only in name.

The magnitude of the problems created by a changeover from a selective to an unselective system was simply not appreciated. Yet Britain was about to undertake an unprecedented transformation of its educational structure. The challenges of developing comprehensive schools were, in practice, left to be solved by each LEA in its own way, in the face of its own difficulties.

Among the LEAs that responded speedily was my own, Brent, where I was head of a secondary modern school. Brent wanted, ultimately, to create a system of 11-18 comprehensives. I was appointed to one of the first of these, Willesden high school, in November 1966, with the school scheduled to open in September 1967.

I had the task in Willesden high school, formed by amalgamating a grammar, a secondary technical and a secondary modern, of planning a comprehensive. Instead of campaigning for a comprehensive, I had the job of organising and running one.

There were serious problems. In Brent, the authority had, regrettably - from expediency, not principles - decided to pay for children who opted out into grammar, denominational, direct-grant or independent schools elsewhere. So a fair number of academically able children were lost to the school.

Although my catchment area, as I used to say, stretched from Rolls-Royce land to slumdom, it was clear we would not have a totally unselective entry. On the contrary, we would become an almost exclusively working-class and increasingly black neighbourhood school. I was not alarmed, as some were, about this. If the job of the comprehensive was, as I firmly believed, to raise the educational standards of the majority, how better to begin than with a school population previously denied full educational opportunity?

Could we really be called comprehensive with such an obviously flawed composition? My answer was, yes, a comprehensive in course of development. If we were to wait for ideal conditions - 100% entry from the local population, a new or suitably modified set of buildings properly equipped, a thoroughly trained comprehensive-dedicated staff and so on we would have had to wait for the Greek Kalends. We had to start with an educational landscape disfigured by the private sector and grammar schools in neighbouring boroughs. We had to get on with the job under the conditions we had inherited.

My instructions were to continue existing courses for all children in the school at the time of the merger. So, while we could organise a comprehensive curriculum for the new entry, for some considerable time we would be running this side-by-side with grammar, technical and modern courses for the majority.

But I was determined to interpret my remit very broadly. I was going to maintain the grammar-technical children's standards and offer them new opportunities, while substantially improving the education available to the modern school pupils.

I began a long process of consultation. I interviewed every member of staff to learn what I could about them and to explain what we would be trying to do. I attended school assemblies and social functions, met the PTA of the tech - no PTA existed in the grammar school, and the one in the modern school was defunct.

No one suggested I should prepare plans for the approval, far less the decisions, of a governing body, or in consultation with parents. The authority made it clear it had appointed me because it thought I could do the job - and I was expected to get on with it. Such a modus operandi would be impossible today.

I had no hesitations about staff deployment. We were one school and would be one staff. Thus my timetable instructions to heads of department were to use all their staff throughout the school, especially for the new entry. There was no reason why modern school staff should not take grammar-tech classes, where able, and it would be good for the others to get used to teaching the slower learners. The children had to get the best that we had to offer.

The new entry would have a genuinely comprehensive education, with everything anyone could reasonably include in a "common core" - science, technical and practical studies, art, music, French, as well as the staple subjects. For nearly all the children, this was a substantial extension of opportunity over what would have occurred under the old system.

Having studied the records of the children in the modern school and, later, seeing the composition of the new entry, I made what I believe was the most crucial decision of all if we were to succeed as a comprehensive. It was to deploy a substantial part of our staffing allocation in creating what was to become the largest remedial department in the country (later renamed special education).

The big problem was getting staff properly trained for the job. Lack of professional expertise had to be compensated for by enthusiasm.

We had no infallible way of deciding admission to a remedial class for the simple reason that no such criteria existed. We decided to adopt a pragmatic approach, including primary school reports and reading tests. Most important, it was essential to recognise that any placement was provisional and what mattered was how, after a while, their teachers estimated each child's ability to cope. The objective was to move children out of a remedial class into the mainstream.

To abolish the remedial department altogether would have been the biggest success of all. Alas, remedial work did not always produce the hoped-for results - permanent improvement of attainment. Children can fall back. We still know too little about how children learn and how to deal with their learning difficulties.

Other problems seemed insignificant beside this one. I outlawed corporal punishment, though not everyone agreed. We began building a highly successful pastoral system. This seems commonplace today, but I am writing of the 1960s, when it was far from common. Those who criticised deployment of staff on pastoral work can have had no idea of how absolutely essential it was if comprehensives were to succeed.

A PTA was organised. I visited all the feeder primary schools to meet the children and their staff and heads. We held meetings for new parents. We opened in September 1967 with what I hoped and expected to be a smoothly running organisation.

Six months later, we held our first speech day, with Christopher Hill, the master of Balliol, an old friend and keen comprehensive advocate, as guest speaker. As I listened to his warm words for what he had seen, I felt relaxed for the first time in 15 months. We seemed set fair for the future.

Five years later, when the first entry had completed the statutory secondary school course, I listened to another guest, Vic Feather, TUC general secretary, kiss the blarney stone ("the best comprehensive school I have seen yet") after I had made my fifth annual report. That had shown conclusively that in exam results, all those who would have been selected for grammar school under the old system had done about as well as they would have done under that system, while the rest - the great majority - had done substantially better.

Whether a school is a success or not depends on many factors. But, I reflected, we had beaten the Cassandras on the one factual criterion they had forecast we could not fulfil. We had proved that while we were advancing the education of the slower pupils, those ahead in the race did not suffer.

· This is an edited extract from The Route to My Comprehensive, by Max Morris, which appears in A Tribute to Caroline Benn: Education and Democracy, edited by Melissa Benn and Clyde Chitty (Continuum, £14.99). Richard Pring will give the fourth Caroline Benn memorial lecture at the Institute of Education in London on Saturday, November 13