As any parent knows, the requirements and expectations of boys and girls are very different indeed, and it is this fact which makes it so important that some schools, at least, continue to make themselves "specialists" in the education of boys.

As any parent knows, the requirements and expectations of boys and girls are very different indeed, and it is this fact which makes it so important that some schools, at least, continue to make themselves "specialists" in the education of boys.

To see why this is so, it is important to consider the nature of adolescent culture as we face the new millennium. You have only to watch a few hours of teen-focused television or to look at the often brilliantly persuasive magazine or billboard advertising to see what unsustainable pressures are currently placed on young people today - and most of these pressures are to do with the way they look, the way they consume, the way they fit in.

The appalling effect this can have on girls is well-documented, but its impact on boys is powerful, too. Whereas the co-educational schools of the 1950s existed in a world of comparative innocence and firmly applied social and moral expectations, for young people in the year 2000, things are more complicated. There is much more knowingness but much less security, and this is where an all-boys school can do so much that is positive and good.

The behaviour of boys at a mixed school and at a single-sex school is noticeably different, especially in the crucial years from 11 to 16 or so. These are the years when many boys can seem most out of their depth with the opposite sex and most likely to mimic the macho posturings which seem to work with those few among them who are more naturally at home in the ill-defined world of adolescent and pre-adolescent courtship.

Often, the more ill at ease a boy is in the company of girls, the more he will seek to express his masculinity in unnecessary and self-diminishing acts of silliness, crudeness or ignorance. Without the immediate fear of being weighed in the sexual balance and found wanting, boys in a boys' school can throw themselves into an enjoyable routine of a wide range of activities.

There is a lack of self-consciousness about the daily lives of boys in a well-ordered single-sex school which makes them loyal to their school, as well as very happy within it. A good school does not harry and bully children towards the disillusionment of adulthood, but preserves the sense of joy to be gained from kinship, playfulness, idealism, hard work and play.

A really good boys' school will employ staff who will have a natural aptitude for teaching boys - a pleasure in the liveliness and zest of their charges, a patience in the face of their endless capacity for forgetting simple instructions, and an understanding of the way that bright boys can astonish us with their swift, lateral thinking and their memory for complex detail. Boys need clear targets and their natural competitiveness needs to be harnessed so that they achieve real success. Formal testing during the course is necessary for boys, who might otherwise put everything off, and excellent university and careers advice helps to focus their minds on where their studies are leading them.

Boys respond to lessons in which they are fully involved and where their own contributions help to shape the outcome of the lesson. Boys may look as if all they want to do is shout, fight or push each other over, but a single-sex school is just the place to find that they usually have another side to them. Conscientious house or form tutors are the best way of ensuring that the pastoral needs of boys are met, just as they are a means of ensuring that there can be no suggestion within the school community of loutishness, bullying, or the belief that work isn't "cool".

Naturally, many good boys' schools will have valued links with local girls' schools. Certainly, this is true of the school where I am headmaster, and girls join our boys for Combined Cadet Force, debating and drama. Boys are not at all deprived of opportunities to meet girls both formally and informally; it is just that - when it comes to study and play at school - they can feel quite free of the pressure to be as the advertisers in FHM or Loaded want or imagine them to be.

The 20th century began with women fighting for the right to vote. This century begins with males fighting for their future. At a time when many of the available male role-models are pitifully inadequate, we find that girls are out-performing boys at every level: the year 2000 is the first in the history of this country when more women than men are in employment.

Boys' schools have long played a magnificent role in channelling the energy, boldness and ambition of young men. It looks as if the lessons they have to teach their communities are more important than ever before.

The writer is Master (headmaster) of Magdalen College School, Oxford. Cardinal Wolsey was made Master of the school 500 years ago this year, and old boys include St Thomas More, Ivor Novello, and - more recently - Oscar-winner Sam Mendes