A 15-year-old male pupil has been arrested after a female teacher was stabbed to death this morning at Corpus Christi Catholic College, Leeds, West Yorkshire police said.
The member of staff at the school in Neville Road, Leeds, was fatally injured this morning. She was named locally as Anne Maguire by students, The Daily Telegraph reported.
West Yorkshire Police detectives said a boy was arrested in connection with the incident and is in custody.
Detective superintendent Simon Beldon said there was no ongoing risk to pupils or staff and that the school was "continuing to operate as normal".
He said: "The situation is under control and officers, including safer schools officers and members of the local neighbourhood policing team, are currently at the school and are liaising closely with staff.
"The rest of the school is continuing to operate as normal and we would ask that parents do not attend the site unless directly requested to do so by the school.
"Our inquiries are at a very early stage but the full circumstances of this incident will obviously be the subject of a full and thorough investigation."
A 15-year-old boy has been arrested in connection with the stabbing
Police were called to the school at 11.48am after they were contacted by the ambulance service following a report that a member of staff had been stabbed.
The teacher was taken to hospital for treatment but was subsequently pronounced dead, police said.
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.
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."
The prime minister 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."
Pupils began leaving flowers at the school gate after which there was a constant stream of children and former pupils paying their respects on Monday evening..
Many of them were in tears. Nichola Davies, 34, broke down as she tried to explain why she had driven 40 miles from Goole to pay her respects.
Mrs Davies, who left the school in 1996, said: "She was just amazing. She was such an incredible lady. It's just so heartbreaking, it really is."
Others laying flowers hugged each other as they placed notes against the metal railings.
The message with the first bunch 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."
There are nearly 1,000 pupils on the roll aged between 11 and 16, according to the school's website.
Tom Riordan, chief executive of Leeds City Council, said: "We are aware of the serious incident at Corpus Christi Catholic College this morning and our thoughts are with all those concerned.
"We are working with the school to support pupils and staff at this very upsetting time. We wish to reassure people that this was an isolated incident and there is no ongoing risk to pupils or staff at the school.
"We are working closely with the police and helping with their investigation."
Russell Hobby, general secretary of the National Association of Head Teachers, added: "We are shocked and saddened to hear the news that a teacher has been stabbed to death at Corpus Christi Catholic College in Leeds.
"Our thoughts are with her family, her colleagues and the students of the school.
"Teachers carry a great weight for our society and we owe them so much. It is terrible that they should be asked to pay this price too. We know that the close community of schools in Leeds will rally round to offer colleagues their support."
Christine Blower, general secretary of the National Union of Teachers, said: "This is a truly awful thing to have happened to a teacher in the course of her work to educate the next generation."