A teenager accused of murdering teacher Ann Maguire in her classroom "has accepted responsibility for the unlawful killing", Richard Wright QC, defending, told Leeds Crown Court.
No pleas were entered and a trial on the murder charge is scheduled to take place in November.
Ms Maguire 61, was fatally stabbed at Corpus Christi Catholic College in Halton Moor on April 28.
Mrs Maguire's death was the first time a teacher has been stabbed to death in a British classroom and the first killing of a teacher in a school since the 1996 Dunblane massacre.
More top news
The Novichok incident in Salisbury has turned into an international diplomatic crisis. But how bad could things get? Adam Shaw reports.
Among those murdered was Keith Palmer, an unarmed constable who "did his job and never wanted any fuss."
Top temperature 14 Celsius (57 F).