The problem has been identified in a number of schools in south London. Police have evidence that the Triads have been successful in drawing in at least two dozen teenagers into crime. They are also investigating reports from children that dozens more have joined up with the Triads and some have extorted money from fellow pupils.
The Metropolitan force'sChinese intelligence unit, which was alerted to the problem several months ago, will today hold a meeting with police youth and community officers to discuss how to tackle the issue. They are concerned that the four Triad societies based in Britain may be copying tactics used by groups in Hong Kong, where schools are considered one of the key areas for recruitment.
The Scotland Yard unit has found that 20 members of a gang in Croydon, south London, aged from 13 to 15, were recruited by Triads through Chinese youngsters. The teenagers, both black and white, have been filmed in central London's Chinatown.
Some children have reported that the recruitment has stretched much further and pupils at south London schools in Lambeth, Lewisham and Croydon are involved.
Head teachers in Croydon are to discuss the issue at their monthly meeting. Bill Whitmarsh, head of St Mary's Roman Catholic school in west Croydon, said: "Evidence of gang existence at a low level was noticed in this school four months ago when action was taken over a dozen boys, their parents were informed and pupils were warned to let their parents and teachers know if they had any information. Since then there has been no evidence of activity in this school.
"The police say that the numbers are between 50 and 150 for the whole of the borough."
Pupils outside the school yesterday were reluctant to comment but one 12-year-old said: "There have been quite a lot of fights, as many as three a week. I have a friend that gets beaten up and he's frightened." Another boy said: "A boy in my class got beaten up but he doesn't like speaking about it because he's scared of them."
There are an estimated 200 hardcore Triad members in Britain who are involved in crimes such as extortion, gambling, vice, counterfeiting and illegal immigration. They operate in Chinese communities, particularly in Manchester, Glasgow and London.
Detective Inspector Andrew Rennison, head of Scotland Yard's Chinese intelligence unit, said: "The pattern in Hong Kong is that youngsters get sucked into Triad societies. They get them involved in an apparently harmless youth organisation but they gradually take part in crime which can later be used to blackmail them."
He said the group believed to be responsible for the activity in Croydon are the Wo Shing Wo society, based in London's Chinatown. Mr Rennison said their influence has dropped recently. "They have had problems recruiting and using teenagers could be a tactic they are now using," he said.