The tragic death of the headteacher Philip Lawrence, from a single stab wound to the heart, has focused the nation's attention on the everyday dangers faced by teachers in inner-city schools. The weekend newspapers were full of knee-jerk analysis articles which attempted to provide answers to questions about the causes of the killing and whether anything could have been done to prevent it.

What is now needed is some quiet reflection and time to consider the state of our inner-city schools and what actually can be done to improve them.

I have spent much of my 30-year teaching career in deprived inner London schools working with boys whose home background left much to be desired. In Hackney, Walthamstow, Peckham and Brent I have taught boys who have been reared in families and on estates where violence is as much a part of their lives as the air they breathe.

Not surprisingly, such boys can bring the attitudes and behaviour they develop in such a climate into their schools, and when they do teachers are left to cope with the aggression that inevitably surfaces.

The reported facts which led up to the stabbing of Philip Lawrence come as no surprise. Two boys fight, one gets hurt and does not like what has happened, so he brings round some of his mates to exact revenge. The story is so familiar to teachers in inner London schools that they could write the script in their sleep.

But the fact is that the situation has been like this for years, and for years teachers have risked their physical well-being to minimise the damage of the flare-ups. Philip Lawrence was carrying on the tradition of London teachers trying to protect their pupils. Like so many before him, he showed admirable courage.

Yet, despite Friday's tragedy, the general level of violence has been low and schools are often able to contain and minimise aggression. By taking a strong line about right and wrong, just as Philip Lawrence did, inner-city schools can provide a haven for boys trying to escape the chaotic lives they have to live.

School is the only stable point of reference for these boys, and, although a macho climate increasingly makes them openly resentful of being pushed to apply themselves, deep down many know that education is their only certain route to a better life. That is why the likes of Philip Lawrence are so desperately needed: men and women who are prepared to give everything to raise the educational expectations of their pupils and their parents, and to explain to the rest of society just what these youngsters are capable of.

Just because most of our inner-city schools are places of order does not mean we can sit back and be complacent. They need help in abundance.

Despite what Gillian Shephard might say, many of them are desperately underfunded. Buildings are in a poor state of repair and in need of immediate attention. It has recently been shown that the condition of the school environment is very much related to improving learning standards.

On the day of his murder, Philip Lawrence expressed to a local journalist the sentiments of all headteachers in inner-city schools: "Our biggest worry," he said, "is the street life outside the school. We try to make sure the undesirables do not get in."

In recent years the street life outside the school has become increasingly fraught with the dangers of our big cities. The emergence of drugs to be disseminated among schoolchildren has heightened tensions, and some of the aggression that we see among young people is drug-related. Some drug pushers see schools as places where they can make easy money and they are on the lookout for inside distributors. Arguments and fights are the consequence of the money that is exchanged for drugs.

What cannot be denied is that an increasing number of inner-city boys are carrying knives. When questioned, they will tell you it is for self- protection against the muggings that are carried out in our city streets. Most genuinely believe that, despite the statistics, there is a real chance they will be stopped, robbed and beaten.

The knife gives them some sense of comfort. Unfortunately studies show that, even in the absence of muggings, those carrying knives are more likely to use them to settle scores which might have previously been settled with fists. As we saw on Friday, the knife is far more lethal than the fist. So any action that is taken to deal more severely with the possession of open blades must be welcome.

Some of the other suggestions being made to improve school security will have limited effect. Security lighting will be more likely to prevent damage to school buildings than acts of physical aggression: most children still go to and from school in daylight. Security cameras might have greater impact, although this is not guaranteed. It is debatable whether those responsible for the killing of Philip Lawrence would have been thinking clearly about their chances of being caught on camera. If they were, they would merely have found another place to attack the boy who was their quarry.

When all the short-term measures have been taken in response to Philip Lawrence's death, we may be able to embark upon a more rational debate about the underlying causes of school-age aggression. Social deprivation and the widening gap between the rich and poor in our society is storing up a deep well of resentment among our inner-city youth. My own lengthy discussions with such boys suggest that they are more politically aware than we give them credit for. They smell the stench of hypocrisy in political support for fat cats lining their pockets on a daily basis while some of their own families can hardly scrape together enough money for life's basics. They are also beginning to perceive that life in Britain might be conspiring against boys and their future prospects. It has not escaped their notice that girls are outperforming them academically, and that jobs are much more easily obtained if "you wear a skirt", as one boy explained to me. Under such conditions, lawlessness for some becomes a way of expressing their identity.

As we mourn the passing of one of our most dedicated colleagues, we teachers can only hope that the memory of his good works will bring about some attitudinal changes in society at large. If Philip's death makes people see just what a hard task the teachers of today are presented with, then some good will have emerged.

If it also concentrates minds about the diminishing status of teachers in this country, then we might see some belated action to improve matters.

The writer, headteacher of Rutlish school in Merton, has had long experience both as a teacher and governor in inner London comprehensives.