A 15-year-old boy has been arrested after a long-serving teacher was repeatedly stabbed to death at a school in front of her pupils.
Tributes have been paid to the teacher, named as 61-year-old Anne Maguire, who was fatally injured at Corpus Christi Catholic College in Leeds this morning.
West Yorkshire Police detectives said the arrested boy is in custody.
Chief Supt Paul Money said teachers at the school, on Neville Road, held the suspect until police arrived, shortly before midday. The teacher died later in hospital.
He said: "A 15-year-old male pupil from the school was detained at the scene by other members of teaching staff immediately after the incident occurred.
"The alarm was raised by students in the school, some of whom witnessed the offence."
He said a knife had been recovered and added: "There were a number of stab wounds to the lady in question."
The Prime Minister tonight joined current and former pupils in paying tribute to a "legend" teacher, described by many as a "mother figure" at the school.
David Cameron said: "My thoughts are with the family of Anne Maguire, as well as the staff and pupils of Corpus Christi school, where she was stabbed to death."
A collection of flowers has already begun to build outside the school gate.
One message read: "To a special teacher. We was all sad about it. I will never forget you."
Kerrianne Ayward, 17, said: "She was just lovely. She was helpful and caring and you could have a laugh with her.
"She was always there for you, even if she didn't know you very well. No one had a bad word for her - I mean no one."
Kerrianne, who left the school two years ago, said: "She's been my referee for everything, college, everything.
"There's no one else you would go to who's better. She was the heart of the school."
Another former pupil, Peter Masefield, 18, said: "I just can't understand why her. Of all people. She was the school's figurehead."
Pupil Georgina Kilroy, 16, said the woman had been a teacher for 40 years.
Speaking outside the school, she said: "I don't know anyone who didn't like her. She was spot on. You couldn't ask for a better teacher."
Georgina said her teacher broke down when she told the children the news. She said that before then they were told a teacher had gone to hospital but lessons continued.
Laying flowers, former pupil Aine Arnold, 17, said: "It's more like losing a family member than losing a teacher.
"As long as we were happy, she was happy. She would do anything for you.
"She helped me personally a lot. She's going to be such a loss to the school. Hers were one of those lessons you didn't want to miss.
"She was just lovely. She was wonderful. I am devastated."
Writing on the website RateMyTeachers.com, one former pupil said: "She's like the school's own mother! Can be very strict but if you're nice to her she will always be there for you, a great woman!"
Another added: "I think she's a good head of year, she's always there if you need someone to talk to :)"
Leeds school stabbing: Live coverage after Corpus Christi Catholic College pupil arrested following teacher's death
Writing on a Facebook page dedicated to the school, contributors described the teacher as "a legend" and a "lovely lady".
Teaching unions described the incident as "awful" and "appalling", and pledged their support.
Leeds City Council said it was working closely with the police and helping with their investigation.
There are nearly 1,000 pupils on the roll aged between 11 and 16, according to the school's website.
It also has "a strong Christian and community ethos".
The website adds: "The school has a very good pastoral structure, which it is committed to keeping and teachers receive very good back-up support."
Hilary Benn, Labour MP for Leeds Central, described the incident as "profoundly saddening" but said he was not in favour of stringent security measures that would keep staff and pupils "behind high fences".
He told BBC News: "Most people are good and most people try and do the right thing.
"This is not representative of the college, of the community that surrounds it, the families that send their children to school and the city itself. But it is profoundly saddening."
He added: "Schools are places of learning. We want our schools to be open - we don't want to lock pupils and staff behind high fences."
Education Secretary Michael Gove said: "This is an appalling tragedy. My deepest thoughts go to the victim's family, her colleagues and the pupils at Corpus Christi Catholic College."
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