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.
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Guillier conceded a "severe defeat" defeat to his supporters as the result came in.
The outage struck Hartfield-Jackson Atlanta International Airport at around 1pm local time, stopping all outgoing flights.
It will be a chilly day for many parts with the highest temperatures, about 10 Celsius (50F) in the far northwest.