There have been no national figures on school violence since 1989, when Lord Elton carried out an inquiry and told the Government that 2 per cent of the country's 400,000 teachers had reported facing physical aggression.
But it is known that expulsion of children from schools - in most cases for violent or disruptive behaviour - is rocketing in this decade. In 1990, 2,900 children were excluded; this year 14,000 are expected to be told to leave.
The number of teachers asking for help from the second biggest teaching union, the National Association of Schoolmasters / Union of Women Teachers, because they were being forced to teach dangerously violent children, has doubled this year to 34.
Drug-dealing, assaults and extortion are now routinely confronted by education and social service authorities increasingly unable to decide what to do with the most difficult children in the country.
Parents, too, are adding to the problem in some schools. Earlier this year the National Union of Teachers said that 20 teachers a month were being assaulted or intimidated by parents in London schools.
Most disputes were over pupil discipline, with some parents attacking teachers who their children said had punished them. One teacher was so severely beaten by a father after intervening to protect a female colleague that he was invalided out of the profession. The majority of assaults were by mothers picking on young women teachers.
Permanent expulsion of really difficult children is often the only option for heads who cannot use the cane, but it starts a vicious circle: social services departments and police say that many children excluded and sent home are out of control and left to roam the streets, getting involved in drugs and crime - often outside their old school gates.
If other schools will not take them, they are meant to receive lessons at home. But the home teaching can be as little as half an hour a day and many children play truant.
The crime caused by having thousands of children permanently on the streets has prompted high-level police concern. In his controversial attempt to launch a crackdown on muggers last summer, Sir Paul Condon, the Metropolitan Police Commissioner, warned that his evidence showed that young muggers were usually either unemployed or had been excluded from school.
Birmingham City Council, which has seen teachers in two of its schools go on strike after they were forced to teach violent children, also warned of the dangers of violence.
Some children liked being excluded because it made their friends think they were macho, the council warned. But if the country allowed them to fall outside the system it would be "creating a 'fifth column' in our midst which will threaten all our future prospects".
Although the evidence was growing yesterday that the violence that engulfed Mr Lawrence had its origin in a dispute between pupils inside the school, several commentators laid emphasis on the fact that it took place outside the gates
John Sutton, general secretary of the Secondary Heads Association, said: "St George' school, like many others in this country, was for its pupils a place of safety, a haven of retreat and good education in a hard and difficult world. It was that outside world spilling over into the world of school which led to this tragic loss."
Paying tribute to Mr Lawrence, Mr Sutton said: "He was certainly a brave man. He certainly wasn't foolhardy.
"I think every head and deputy head in the country will recognise the situation he found himself in. Many will say, 'There but for the grace of God go I.' "
Harry Greenway, Conservative MP for Ealing North and a former headmaster, said: "This does not relate to school discipline at all. It is gang warfare and that is what needs to be tackled.
"There are rival gangs in various parts of London. It has gone on for a long time and has got much worse.
"It would be dreadful to say that school discipline has broken down, particularly in this school where it is known to be very good."Reuse content