Folajimi Orebiyi, known as Fola, was stabbed in the neck outside Aston House Estate in west London on 3 July 2016.
The 17-year-old fled along the Portobello Road but collapsed. An air ambulance was called but he was pronounced dead at the scene.
The youth, who cannot be named for legal reasons, wept as he was sentenced at the Old Bailey.
Fola's mother Yinka Bankole described her son as "a vibrant and intelligent young man, with a bright future ahead of him" who was looking forward to going to university to study maths and physics.
"We are still trying to process the fact that our beloved boy is no longer with us," she said in a statement on behalf of the family.
Fola's young brother said he was his best friend and asks for him every day, she added.
"I feel like this tragedy could so easily have been prevented."
Judge Anthony Bate told the young defendant that his carrying a knife in a public street was a "disturbing feature of the case".
The court heard that a friend of Fola had fought with the 15-year-old defendant, exchanging insults in the weeks before the killing.
On the night of his death, Fola and his friends ran into the defendant and his friends near Portobello Road after watching a football match together.
Fola agreed to a fight unaware his opponent was armed with a knife, which the defendant used in an ambush, singling him out and stabbing him in the neck.
A second boy, aged 16, was acquitted of Fola's murder.
A 15-year-boy has been jailed for 13 years for murdering a teenager in an ambush in Notting Hill.