Malcolm Mide-Madariola, 17, was knifed in the heart outside Clapham South Tube station in south London at about 4.30pm on November 2 last year.
His family had moved to Britain from Nigeria for a safer life, but the level of violence means that London is now a less safer place than the day his son was born, according to his father.
Mr Wole-Madariola said he was shocked by the indifference of the two youths involved as he sat through their Old Bailey trial.
He told the Mail on Sunday: "We went to the trial every day and the thing that really upset me was these boys showed no remorse, they were smirking.
"At one point they said, 'it was just a knife, no big deal', but it was. I had four children and now I have three."
Mr Wole-Madariola, 52, was abroad doing research for a degree when his thoughtful, church-going and football-loving son was killed. His family have moved from the home they shared with Malcolm in Dulwich, south London, to Dartford, Kent, since the killing.
Stating that it was the first time he had ever seen his family in pain, Mr Wole-Madariola told the paper: "I felt like a failure. I am a security expert and I had failed at keeping my family safe."
He added: "We thought it would be safer for our children moving from Nigeria to England, but London is not as safe as when my father first moved here in the 1960s. It is not even as safe as when Malcolm was born."
He called for tough sentences on people who are involved in knife crime, and said the parents of youngsters who end up in trouble must also take responsibility for what is happening.
A 17-year-old boy, who cannot be named for legal reasons, was found guilty of murder and possessing a knife after an Old Bailey trial earlier this year.
His co-defendant Treynae Campbell, 19, of Sydenham, south east London, had admitted having a blade but was cleared of Malcolm's murder.
Jurors were told how the killing came two days after an incident at the south London sixth form college where Malcolm was a student.
On November 2, the youth looked for Malcolm's friend, claiming he had threatened him with a knife.
A few hours later, there was a confrontation with the victim's group after college outside the Tube entrance.
After an exchange of words, the youth drew a long curved blade and stabbed the victim three times before running off and discarding the weapon in a bin, jurors heard.
Sentencing is due to take place in July.
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