It is a British disease, Tony Blair wrote on this page last month, to be obsessed with institutions to the neglect of what goes on inside them. True; and the most encouraging thing to me, as I come to the end of a long career in teaching and education, is that at last there are signs that we are beginning to recognise it.

Not, I hasten to say, the newly painted signs at the gates of newly painted schools: “City Technology College” and (pace Mr Blair) “Grant-Maintained” say little about the quality of the teaching in the schools they label, and less than nothing about the value added to the life chances of their pupils. But the signs that a school improvement culture is beginning to take root are tangible and real. The National Commission on Education (launched on a tide of concern that schools were both failing and being failed) identified many of them.

Successful schools, it said in Learning to Succeed, are characterised by positive leadership, shared aims and values, an explicit focus on teaching, learning and assessment, and a commitment to participation. In successful schools (no mention here of league tables or socio-economic rating) pupils participate in their learning, teachers participate in management, parents participate in their children’s education. Successful schools have high expectations of all - the crucial word - of the pupils in them. Last month’s crisp signing-off report, Learning to Succeed: the way ahead, re-emphasised that message.

I believe that schools are listening to it. No teacher, after all, wants demoralised and failing children - but there’s a lot of history to overcome. There is 100 years of education-as-selection, to start with, with teachers as the keepers of the gate, and100 years of the insidious influence of the Victorian public school. There is 100 years, too, of education-as-control (it’s alive and kicking among right-wing politicians, and it lingers on in schools) and 100 years or more, all the way from Thomas Arnold to Miss Jean Brodie, of the damaging myth of the teacher as a sort of moral superstar. And there is what seems like 100 years (although it is only 10) of ill-conceived prescription and subtle, petty denigration.

So there is a certain amount of baggage to be discarded. Nonetheless, the evidence is clear that schools are improving from within. The Office for Standards in Education, for all the spurious certainties that it lays claim to - those instant judgments about precisely how well a class is learning - has certainly helped. (Given its cost, that is the least we could have expected). The inspection framework is an unexceptionable summary of what in the best of worlds we would like our schools to be and the inspection reports themselves have pushed us to think harder about the range of skills that children can exercise and achieve.

In secondary schools they have focused attention not just on the headteacher’s leadership (and it would be difficult now to find the equivalent of the head whom I once knew, who in times of stress would lock himself in this study and take out his violin - Nero fiddling while Rome burned) but on the often underdeveloped management skills of departmental heads.

Even so, it is clear that the isolationism that has bedevilled so many secondary schools (my department, my subject, my classroom, my pupils, my problems) is beginning to break down. Adults other than teachers - support staff, parents, neighbourhood engineers, sixth-form helpers - are playing a much more prominent role. That crucial but indefinable element, the climate of the school, is slowly warming. Far more children are enjoying their education, and opting for more of it when they reach 16. The teacher NCO, barking his orders to the class, is a dying and unregretted breed. All the schools I know are working for improvement.

Why, then, the anger that I feel, after 30-something years of teaching and 20 years of headship, for what is happening inside them? It has something to do with hypocrisy - the peculiarly English disease that Tony Blair forbore to mention - particularly the hypocrisy that currently surrounds parental choice and the issue of class sizes. “Parental choice” in the present circumstances is just a synonym for privilege - another of our national diseases.

Are we serious as a country about the inclusiveness of that explicit ambition of the national commission - that we should have high expectations of all our children? If we are, we ought at least to recognise that choice - convenient shorthand for market forces - often runs counter to it. The stress on market indicators - A-level points, GCSE grades A to C, complex league table ratings - conveys a subtly different message. Difficult pupils, that message runs, are expensive, uneconomic, a poor investment. It wasn’t totally surprising that in OFSTED’s recent list of high-performing schools, a significant number showed a worsening of performance in examinations A to G. In market terms that clearly didn’t matter. Yet on any objective consideration, it is our inability as a country to educate our weakest pupils that is our most conspicuous failure. Logically, it is their performance we should be reporting in league tables, but parental choice won’t wear it.

The theory is that market forces make the weak grow stronger. They don’t. In education they create sink schools as surely as we created, in the grammar schools where I started my career, sink streams: populations of children with the educational odds carefully stacked against them. In such schools the rhetoric of school improvement rings hollowly, if it rings at all. Shared aims and values? A focus, always, on teaching, learning and assessment? Parents participating in their children’s education? Try telling that, headteacher colleagues say, to teachers struggling with criminality, alienation and neglect. Their major preoccupation is to create, however briefly, conditions in which some learning can take place. You can hardly blame them if they feel that their concern for those children’s chances is poorly matched by the world outside.

The second hypocrisy is about class sizes. Academics who specialise in school improvement - some teachers smile at that - tell us (and I believe them) that class sizes are not the critical factor where the success or otherwise of teaching is concerned. Given that the pupil-teacher ratio in state schools has worsened annually since 1990, is at its highest now since 1983, and is set inexorably to go higher still, that makes convenient news for politicians - all the more so, given that the PTR in independent schools has improved each year since 1970. Three cheers for market forces.

But the point about large classes is not that they necessarily make the teaching worse, but that they make it a great deal harder. Larger classes mean more assessment, more reports, more differentiation - more of whatever problems those children bring into the classroom with them. It is beyond dispute that those problems have increased to a frightening degree in the past 10 years. Add all of that to the proper pressures of accountability and the shelves of spurious legislation, and you get an unstable and disturbing situation.

What’s most at risk, in every school, is the drive for school improvement. I’ve worked for that, in different schools, for nearly 30 years, and I trust that I have learned a little in the process. There are two essential ingredients omitted from the national commission list. More than anything, school improvement needs energy and time: energy (for example) to set up the extra-curricular activities that create a climate of shared commitment and enjoyment; time to watch each other teach, and share as teachers the lessons that we learn.

Teachers, in my experience, have been astonishingly generous with both, but when I look at the faces of my friends and colleagues in our school, I know that their reserves are running low. One of them - a crucial player in the changes we have made to lift the performance and self-esteem of all our students - indirectly told me so. “What worries me most,” he said, “is that at times I feel like the carthorse Boxer.”

I picked up his copy of Animal Farm and looked the reference up. “Clover warned him sometimes to be careful not to overstrain himself, but Boxer would never listen to her. His two slogans, ‘I will work harder’ and ‘Napoleon is always right’ seemed to him a sufficient answer to all problems. He had made arrangements with the cockerel to call him three-quarters of an hour earlier in the morning instead of half an hour. And in his spare moments, of which there were not many nowadays, he would go alone to the quarry, collect a load of broken stone, and drag it down to the site of the windmill unassisted.”

So that’s what teaching now feels like, I thought. And then I thought: I’ve enjoyed my career enormously. I wish it could have finished, though, on a more optimistic note.

Michael Duffy is retiring this week as headteacher of King Edward VI School, Morpeth, Northumberland.