Ann Maguire's killer suffers from a personality disorder, Leeds Crown Court has heard.
Experts unanimously agreed he had the condition but Richard Wright QC, defending him, said: "Plainly, these were the actions of a deeply disturbed young man."
The 16-year-old is expected to be sentenced shortly for the unprecedented murder, which is the first time a teacher has ever been killed in a British classroom.
The judge who presided over the Ann Maguire murder trial has slammed 'ill-informed commentators' who criticised him for naming Will Cornick.
A teenager who has admitted murdering his teacher came from a loving home and was thought of as a good student and in many ways normal.
Ann Maguire was just months away from retirement when she was stabbed to death in front of horrified pupils at a school in Leeds.