The recent London conference held to mark the final report of the National Commission on Education caused me to reflect, once again, on the vexed relationship between social and economic disadvantage and educational achievement - or the lack of it. There is little consensus on this relationship: poverty, unemployment and school performance seldom relate together in universally agreed patterns of cause and effect.

What must be obvious to anyone living in urban - but also in many rural - areas are the abject living conditions of some families. Poor housing, parental unemployment and the absence of well-advertised consumer goods creates, for a high proportion of school pupils, the fear of humiliation and anxiety about the family making ends meet.

Of course, these factors do not necessarily influence the outcomes of schooling: many young people succeed in spite of them and many families remain committed to the education of their children regardless of their disadvantaged circumstances. But for some, social and economic disadvantage may have serious educational consequences.

Thus those children without any nursery or play school experience begin schooling at an immediate disadvantage in comparison to their more fortunate peers. Those whose parents are distracted and worried constantly about debts will be less likely to receive help and support. Pupils without pocket money for school trips or lacking the right football club strip, designer label clothes and trainers - so valued by image-conscious young people - may be embarrassed and inhibited in the school and in their peer group.

The questions I posed at the national commission conference were whether we are making too much of the educational consequences of these disadvantages. Have they become an excuse for low expectations and poor teaching? Is there an over-awareness of the potential consequences of social disadvantage amongst teachers? Is there a danger that teachers too frequently over-generalise from disadvantage to incapability? Can a coalition of lower expectations be created between the parents, the community and the school?

My answer to these questions is that we might indeed be confused about disadvantage and, as a result, we may be encouraging its use as an excuse. In some schools teachers appear to be doing just that. They blame the negative influence of the neighbourhood, the anti-school attitudes of the families, and the pupils’ limited abilities for the lack of achievement; all factors deemed to be outside of the control of the school and, therefore, beyond the scope of good teaching. Some teachers react by adopting social-worker roles and endeavouring to support the pupils’ families; some are drawn to political protest.

I do not wish to minimise, in any way, the potency of poverty or any other disadvantage to affect negatively the lives of both pupils and teachers. I have worked both in and with schools where pupils have had to cope with all the factors which I listed earlier and where teachers have exhausted themselves in their efforts to improve the quality of the lives of their pupils. I do believe, however, that the most effective way for teachers to seek to help their pupils is by enhancing their learning opportunities by making the school more effective.

What must be remembered - it was clearly acknowledged by the House of Commons select committee on education - is that, while pupils from families which are severely socially or economically disadvantaged do succeed in school, it is undoubtedly much harder for them to do so. The evidence collected over many years by the Inner London Education Authority shows that a substantial proportion of children face not just one but several disadvantages throughout their childhood and that the impact of such factors is cumulative.

It is in these circumstances that the energy and dedication of skilled teachers can be most fruitful. More advantaged pupils are able to draw on their families for support; the disadvantaged rely much more heavily on their schools. Both research studies and Her Majesty’s Inspectorate reports, however, also make it clear that it is much harder for teachers to succeed in schools with high proportions of disadvantaged students: they become tired and discouraged; excessive pastoral work with pupils and parents absorbs too much energy; dealing with social services, other care workers and the police distracts them from their teaching.

School improvement, in my judgement, offers the most acceptable way to challenge the excuse hypothesis. We know that some schools succeed against the odds as the research on school effectiveness, most recently supplemented by 12 case studies carried out for the national commission (to be published in the autumn), illustrates. School improvement, however, cannot be a panacea and there is no simple recipe for effectiveness. What it does is enable teachers to work together in a positive way, as a team, rather than feeling that they are failing as individuals or in David Reynolds’ words “projecting their own inadequacies on to the children” (TES, June l6).

School improvement also places the headteacher and the governing body in the driving seat: reviewing the outcome of the school’s OFSTED report and calling on the support of the LEA, university researchers and specialist consultants.

As we know from so many autobiographies, education offers the way out of social and economic hardship. Even in a recession, those with educational qualifications fare better than those without. Inevitably, however, any school improvement that takes place is likely to benefit those from advantaged families - those better able to make the most of new opportunities - more than those from families which are facing difficulties. Thus, though overall national standards may rise, the difference between the most and the least advantaged will probably also increase.

For this reason it is absolutely imperative that the assessment playing field is kept level. If we slip back to norm-related criteria of success, then many disadvantaged pupils will never be seen to succeed. It is only with an assessment system that remains relatively stable that it will be possible to measure any overall progress. Those who automatically greet all positive results with scepticism and the accusation of slipping standards, need to reflect on this point.

I welcome, therefore, both the Secretary of State’s and Tony Blair’s recognition of the need for individual school communities to embrace school improvement. I think this is the only realistic way in which anything other than minor improvements in enhancing the opportunities for learning and for lifting the national standards of achievement will ever be achieved. I also welcome the enthusiastic commitment of my co-speaker at the national commission conference - Tim Brighouse. As chief education officer of a large urban authority, he pledged his support for schools which seek to challenge low expectations.

Encouraging schools to use feedback from Office for Standards in Education inspections as a baseline from which to improve makes a great deal of sense. The national commission case studies illustrate the ways in which heads and teachers can focus much more strongly than has sometimes been the case on learning and achievement. In many schools staff and governors are challenging themselves: asking whether over-protectiveness is inhibiting higher expectations.

Many teachers are also drawing on new interpretations of intelligence - such as those put forward by the American psychologist Howard Gardner - to realise that pupils who crack the code and who suddenly understand the principle of what they are trying to master, gain insight into their own learning styles and who realise they can compensate for their weaknesses by capitalising on their strengths, have actually become more intelligent.

The national commission has produced the best analysis of our education system for many years. If, as a result, we break through the particular glass ceiling that has traditionally segregated the educational expectations and performance of our young people on the grounds of their family’s economic and social circumstances, it will have achieved a great deal. Of course, young people who experience every educational advantage that money can buy will always be likely to exceed the performance of those whose families are poor but, as a society, we may have jacked up our overall standards.

We may even have taken a step towards achieving what the chief executive of the Hong Kong and Shanghai Bank has termed the “missionary zeal for education” that is a characteristic of pupils, schools - and governments - in the Asian Tiger economies.

Professor Peter Mortimore is director of the Institute of Education, University of London.