The boy's defence lawyer, Richard Wright, today said the 16-year-old "accepted responsibility for the unlawful killing" of Spanish teacher Ann Maguire but didn't enter a plea.
The death of the 61-year-old Maguire was the first killing of a teacher in a British school since the 1996 Dunblane massacre in which a lone gunman killed 16 children and their teacher.
Maguire had taught at Corpus Christi Catholic College in Leeds, northern England, for 40 years and was planning to retire.
The boy, who was 15 at the time, appeared in Leeds Crown Court by video link. The court is preparing psychiatric reports before a murder trial expected in November.