Primary heads, it seems, are queuing up to leave a job which is not what it was when they joined. Since 1988 and the arrival of National Curriculum and local management of schools, they have been battling to stay in contact with the classroom, and it is not surprising that many heads in their fifties have looked at their diminishing mortgages and decided that the pension will suffice.

Yet if you visit a lot of good primary schools, you become aware that many effective and optimistic primary heads are still around. It could be argued that they represent a new generation, supplanting the retiring old guard. This, though, would be unfair to the many long-serving heads who have learned how to live in the new educational world, and who possess the resilience and energy to enjoy this hugely demanding job.

Insight into what makes a successful primary head today is provided by Geoff Southworth’s study Talking Heads: Voices of Experience. “Headship is not a job for the faint-hearted,” he concludes, “it involves a great deal of work. .. commitment, concern and dedication.” Two Essex primary heads, Louisa Sliwa and Pam Wells, seem to embody many of these qualities.

Stanway Fiveways County Primary in Colchester, the 290 pupil school where Pam Wells has been head for four years, is a delight to visit: displays are immaculate, the children are open and friendly, the staff are welcoming and the teachers are clearly effective. Ms Wells justifiably admits to being “Proud when parents come in and say that it’s a happy school. That feeling comes through in times of doubt.”

But a school does not get to that point by accident. It has to be led there by an alchemic mixture of assertiveness, sensitivity, guile and professional knowledge. Of course it was always thus, but it is particularly difficult for many of today’s heads to lead from the front because they are not teaching the National Curriculum day by day, as their teachers are, and are distracted by office work.

Indeed, one of Geoff Southworth’s heads said: “I feel disenfranchised because I don’t know the curriculum to the extent that they have to... I’m not in control as much as I could be.”

Pam Wells feels that a head has a broader job, keeping the school on the chosen philosophical track. “It isn’t a dilemma for me. When you become a head you are the one who will be leading and enabling others - the task is to keep at the centre of things. As one of the staff said to me, ‘Just keep putting the signposts out!’.”

The continuous drive to develop the school raises a dilemma for the sensitive head. On the one hand, because he or she runs a collegiate, mutually supportive institution, he or she wants to share with the staff some worries and to be strengthened by their concern and advice. On the other hand, though, taking responsibility is what he or she is paid for, and teachers with worries of their own may not respond well to a head who walks long-faced into the staff room complaining about the pressure.

Last Summer, nevertheless, Pam Wells decided to approach the job in a slightly different way. It had been a difficult term and, “I felt I couldn’t go on like that for another 20 years.” Since then she has, “Opened up the shell a little bit.” She has had, for example, a worrying time over a pupil exclusion. “In the past I would have kept a lot of that inside, but now I share it a little. ”

She has also learned not to bother quite so much about not covering every angle. “There are bits of the job I feel a bit woolly about. At one time I would have worried, but now I know I’ll sort it out in time.”

Further west, in Harlow, Louisa Sliwa, for eight years head of Hare Street Infants, has also learned that one of the secrets of survival is not to worry about everything at once. “I do it in bite-size chunks. The fact that I am responsible for finance the whole time can look daunting. But the year is a cycle, so that in April it’s the school budget and then that sort of subsides. ” She does not regard herself as bogged down by bureaucracy. “We’re not administrators - that’s someone else’s role.”

What is continuous and demanding, though, is the need to make sure the children are learning. One of the most striking things about my conversation with Louisa Sliwa, was that whatever the question, her answer invariably turned into a discussion about working with children in the classroom. She teaches regularly, but she, too, feels that heads start to lose the classroom touch. “You don’t lose your rapport with children, but you get out of being able to organise them so easily.”

In common with Pam Wells, though, she believes that keeping everyone focused on the central approach is more important than being in touch with the detail of the curriculum. Her enjoyment of the job is palpable, and like Pam Wells, she mentioned pride. “We’re involved in the growth and development of people - that’s the most exciting thing about the job and as heads we are enablers of that.”

I was once a primary head, and I claim the ability to recognise a happy school led by someone who feels on top of the job. On the way home I tried to analyse what it was about Pam Wells and Louisa Sliwa that left me feeling so optimistic.

The answer is that both of these women have, for some years now, been focusing relentlessly on the task of improving children’s learning in the classroom, moving steadily from one curriculum priority to the next, refusing to be overwhelmed or distracted. In both schools, short-term planning is a matter for classroom teachers, working in teams. The head’s task is to keep a gentle but insistent pressure on medium- and long-term planning, and to monitor the effects.

Each head has a clear philosophical vision of what school life should be like for primary children, and this vision has been successfully sold to the staff team. And each seemed good at making relationships: with pupils, teachers, education officers, governors and parents. This involves not only the ability to smile and press the flesh, but the courage to be firm - and perhaps unpopular - where the welfare of pupils is at stake.

This is how Louisa Sliwa describes the battle to win proper support for a child with special needs. “After one phone call I was too distressed to go into assembly and I had to ask someone else to do it. I thought ‘What am I doing? I’m fighting for children and they’re not listening to me.’ And I get so frustrated and angry.”

Geoff Southworth, in the final paragraph of Talking Heads writes of “a continuing belief among heads that they can make a difference to the schools they lead.” Pam Wells and Louisa Sliwa obviously both share this belief. The mistake often made by casual outside observers is to assume that it an easy business; that the head has only to speak to make things happen.

Pam Wells indicates how demanding school leadership is by explaining that by the end of term, she is so tired that she finds it increasingly difficult to speak coherently. One day she went shopping after school, “But I found myself dropping my bag and bumping into people - I just had to go home.”

Geoff Southworth writes: “Much is expected of them; they expect even more of themselves.” Good heads must be recognised and listened to, not because they have all the answers but because they, at least, have a fair idea what the questions are.

* Talking Heads: Voices of Experience by Geoff Southworth, Pounds 5.99 from the University of Cambridge Institute of Education, Shaftesbury Road, Cambridge, CB2 2BX