A pupil “winked and smiled” at another pupil just before he stabbed teacher Ann Maguire to death, an inquest has heard.
In statements read out in court, a pupil described how killer Will Cornick offered to show them “how sharp” the knife was.
One teenager said Cornick attempted to disguise the knife by placing it up his sleeve but then decided to put it in his blazer pocket.
The boy said Cornick then went next door where Mrs Maguire was teaching.
“He just winked and smiled at me as he left the room,” he said.
Another pupil at Corpus Christi Catholic College, Leeds, said Cornick told them how he would “stab her in the neck, because it was a certain kill”.
One of the children told Cornick he needed help, but he replied: “If you go and get someone, I’ll do it faster and I’ll get you too.”
Nick Armstrong, the barrister representing Mrs Maguire’s husband, told the inquest one of the key issues was why none of the children reported what they were told on that day – 28 April, 2014.
A witness said: “In a high school, someone saying they’re going to kill a teacher is just a joke.”
The inquest heard previously that the “intelligent” but “weird” Cornick had clashed with Mrs Maguire after she refused to let him drop Spanish.
In November 2014 he was jailed for life for murder and ordered to spend at least 20 years in custody.
The inquest continues.