An Old Bailey jury found Nathan Brown - leader of a schoolboy gang which based itself on the Chinese triads - guilty of murdering 14-year-old Carl Rickard with a machete at the gates of Kidbrooke School in the London borough of Greenwich.
Nick Williams, head of Thomas Tallis in Greenwich where Brown was a pupil at the time of the attack in January said: "Schools cannot be held responsible for everything that happens in society.
"Teachers are not social workers and they cannot patrol the streets. What they can do is create a climate within school where young people receive support and feel able to discuss their problems.
"There is a danger that people invest in schools expectations that cannot be met, but what we need is the concerted efforts of external agencies such as counselling services."
Mr Williams pledged to redouble his efforts to create an environment at Thomas Tallis which would allow children to talk about their problems.
Brown, who led a gang called the Golden Snakes, is believed to have carried out the murder as revenge for a slight his gang had received earlier in the week.
He was said to spend hours alone in his bedroom playing computer fighting games and reading martial arts literature bought in London's Chinatown in Soho.
According to Mr Williams, pupils don't see school as a place where they can come with their problems even when a team of counsellors is on site offering help to children with difficulties.
He said: "Young people getting into the wrong company and making the wrong decisions is a significant problem. You can give it whatever name you like, it is the same problem - young people mixing in the wrong way."
His view was shared by Patricia Jaffe, headteacher of Kidbrooke School where Carl Rickard - known as "CJ" - was a pupil.
"The youngsters who find themselves getting involved in criminality are those looking for somewhere where they can gain a sense of themselves, but we need to support these youngsters so they can find this identity at school," she said.
Headmaster Phillip Lawrence was knifed through the heart when he went to help a pupil attacked by a triad-style gang outside St George's Roman Catholic School in Maida Vale, North London. A separate triad-inspired gang was involved in the non-fatal stabbing of John Mills, 59, husband of the director of public prosecutions, near his home in north London.
Police played down the significance of the gangs. A spokeswoman said: "We are not aware of a problem with triad gangs but we are monitoring the situation. Talking about triads will give the name credence and we don't want to do that."