Five teenagers were given long sentences of detention 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 15-16 at the time, killed Zac outside Park Campus School in West Norwood, south London, in July last year.
Helder Demorais, 18, Ricardo Giddings, 17, Jamal Moore, 17, and Kyle Kinghorn, 18, were found guilty of murder and ordered to be detained during Her Majesty's Pleasure.
Giddings was given a minimum term of 18 years, Kinghorn 16 years, Demorais 16 years and Moore 14 years.
Shaquille Haughton, 16, was found guilty of manslaughter and was detained for eight years with an additional four years for wounding Zac's friend, making a total of 12 years.
The youths, who were all from south London, all had a previous conviction for having a bladed article.
Judge Giles Forrester told them: "This was gang related, going together to hunt down your victim like a pack of hounds.
"It was a vicious, shocking and sickening case of violence outside a school at a time when pupils and staff were gathering at the start of a school day."
Zac had been "mercilessly" chased as he "fled for his life".
"There were two young victims, each stabbed outside or near his school at a busy time for pupils and teachers alike," added the judge.
Edward Brown QC, prosecuting, told the trial: "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 bayonet-type knives and were driven to the school in a stolen car.
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 on 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.
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 spoken at a Youth Against Violence conference the day before his death, and was seeking help to turn his life around.
"He told me he wanted to help young people facing the same problems," said Mrs Olumegbon.