Mrs Maguire, 61, was stabbed in front of her pupils at Corpus Christi Catholic College in Leeds.
Leeds Coroner’s Court yesterday heard her jugular vein was severed in the attack on 28 April, as an inquest into her death was opened.
A 15-year-old boy has been charged with Mrs Maguire’s murder.
Detective Chief Inspector Nick Wallen, of West Yorkshire Police, told the inquest the teacher had suffered a number of stab wounds but one to her neck, which severed the major vein, was the fatal injury.
He told coroner David Hinchliff that the emergency services were called to Corpus Christi at 11:49am on the morning of the stabbing.
The officer added: “They were directed to the top-floor modern languages department where paramedics initially attended to Mrs Ann Maguire – a teacher at the school – who was very seriously injured having been stabbed.
“Mrs Maguire was taken by ambulance to Leeds General Infirmary for emergency treatment. Sadly, she did not survive her injuries and her death was pronounced at 1:10pm.” He told the coroner’s court that Home Office pathologist Brian Roger conducted a forensic post- mortem examination on the same day at Pinderfields Hospital, in Wakefield.
Mr Wallen told the coroner: “Dr Rogers established Mrs Maguire’s cause of death as shock and haemorrhage.
“Although there were a number of stab wounds, a stab wound to her neck had severed her jugular vein and that was the fatal injury.”
He said a second post-mortem examination came to the same conclusion.
Mr Hinchliff heard Mrs Maguire’s body was identified by her husband, Don.
The coroner issued a burial order and released the teacher’s body so a funeral can now take place. He also asked a police family liaison officer present in court to pass his condolences on to Mrs Maguire’s family.
Mr Hinchliff adjourned the inquest to a date which has yet to be arranged.
Mrs Maguire worked at Corpus Christi, in the Halton Moor area of Leeds, for more than 40 years.
None of her family was in court yesterday for the first day of the inquest.
She was due to retire in September and, last year, the school celebrated her four decades of service.
Headteacher Steve Mort has said she was the “mother of the school”.
Tributes to the teacher flooded in from around the world and a 100-yard collection of flowers, messages, photographs and other mementos stretched from the gates of Corpus Christi to the church next door.
Mrs Maguire lived in the Moortown area of Leeds with her husband, who is a landscape gardener and former teacher.
She had two grown-up daughters, Emma and Kerry, and two nephews who she brought up as her own sons after the death of her sister nearly 30 years ago.
The teenager charged with the teacher’s death was remanded in custody and is due to go on trial later this year.