Five teenagers will be sentenced today for killing a 15-year-old boy who was stabbed to death as he arrived at school.
Four of the youths were found guilty of murder and one of manslaughter last month.
The Old Bailey heard that within moments of being hounded down, Zac Olumegbon lay dying on his back in the garden of a house just metres from the school.
He had been stabbed four times, two of the wounds piercing his heart.
The killers, who were aged 15-17 at the time, killed Zac outside Park Campus School in West Norwood, south London, in July last year.
Edward Brown QC, prosecuting, said: "He found himself hounded down and killed.
"He had only just arrived at his school that morning. He was killed a matter of metres from it."
The youths were armed with at least two knives and had deliberately been driven to the school to attack Zac, jurors heard.
Another young boy was injured in the confrontation but all the signs were that Zac was the "prime target", said Mr Brown.
He added: "The reality of the events that were to lead to Zac's death is that it had its origin in the dreadful but certain fact of rivalry between young gangs.
"Needless posturing that on occasion led to violence and occasion serious violence and death.
"It was a tragic and terrible waste of a young life."
Mr Brown said the defendants were members of the GAS (Guns And Shanks) gang from Brixton.
Zac was associated with the rival TN1 (Trust No-One) gang from Tulse Hill.
"Zac was a member of it and was known as Little Zac," said Mr Brown.
Helder Demorais, 18, Ricardo Giddings, 17, Jamal Moore, 17, and Kyle Kinghorn, 18, were found guilty of murder and face life terms.
Shaquille Haughton, 16, was found guilty of manslaughter.
The youths will also be sentenced for wounding another schoolboy in the attack.
Zac's mother Shakira told the court of the pain of losing her youngest child.
In a statement to the court, she said: "The scene that confronted me when I reached the school is indescribable.
"Even though Zac was young, he touched many lives."
She added: "This is our life sentence. It feels like the 15 years I spent raising my son and all the hopes and dreams I had have been in vain.
"I never thought I would bury any of my children, let alone my baby boy.
"He was snatched away in such a cruel and heartless way."
She said Zac had attended a conference which was helping him turn his life around.
"He told me he wanted to help young people facing the same problems," said Mrs Olumegbon.