A teacher has broken down in the witness box as she recalled how youth footballer Kiyan Prince lay bleeding on the ground after being stabbed.
Kiyan was a striker for QPR's youth team
Liejhe Hernandez said she called for help after a play fight outside the London Academy in Edgware, north London, began to get out of hand.
A 16-year-old boy denies murdering Kiyan after he tried to intervene in the incident, but admits manslaughter.
Ms Hernandez told the Old Bailey she helped tend the QPR youth striker, 15.
She said it was not immediately clear how seriously he had been injured.
In tears, she added the boy involved in the fight with the defendant was "holding a shirt over one of Kiyan's arms".
Ms Hernandez told the court: "I saw it was bleeding. I told him to put pressure on the wound to the arm.
"He lifted Kiyan's shirt and jumper. I saw a little nick on his chest and told him to apply pressure to that."
The teacher said she had been on gate duty as the school day ended on 18 May when she spotted two boys apparently play-fighting just outside the grounds.
She used her mobile phone to call the deputy head and when she turned saw the boy tending to Kiyan on the floor.
The court was told the boy - referred to as witness A - was asked by police whether he thought the defendant had been playing around when the fight started.
"I wanna say he was playing about but I think... he knew... his friends were watching him," he told officers.
The defendant, who cannot be named because of his age, had been banned from the London Academy at the time of Kiyan's death, the jury heard.
He told police he had used a "little toy" knife but intended to leave "just a little scratch...".
The trial continues.