A 15-year-old boy has been arrested after a woman teacher was stabbed to death at a school.
The teacher, named locally as Anne Maguire was fatally injured this morning.
West Yorkshire Police detectives said a 15-year-old boy, a pupil at the school, was arrested in connection with the incident and is in custody.
Ms Maguire was a long-serving member of staff at Corpus Christi Catholic College, in Neville Road, Leeds.
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.
Ms Maguire was taken to hospital for treatment but was subsequently pronounced dead, police said.
Staff and pupils expressed their shock at the death.
Pupil Georgina Kilroy, 16, said Ms Maguire 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.
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 :)"
Writing on a Facebook page dedicated to the school, contributors described the teacher as "a legend" and a "lovely lady".
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."
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.
"Appalling events like this are thankfully very rare indeed but the death of any teacher in her place of work, which should be a place of safety, is devastating. Our condolences go to the family and friends of this teacher, and to students and colleagues at the school.
"The NUT will provide any help and assistance we can possibly offer to Corpus Christi Catholic College and its community."
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."
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."
Downing Street described the stabbing as "appalling".
"The Prime Minister's thoughts are very much with the victim's relatives as well as the entire school community there, which I'm sure will be deeply shocked," the Prime Minister's official spokesman said.
Pupils began leaving flowers at the school gate.
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."
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."
Samuel Dasaolu was a pupil at the school until 2011 and paid tribute to the teacher, who taught him Spanish and Religious Education.
He said: "I felt like she was almost a mother figure of the school. I felt I could go and talk to her. She made everybody feel so comfortable."
The 18-year-old said he never heard about pupils carrying weapons when he was at the school.
"I can't get my head around the fact that somebody would do that. Everybody loved her and respected her," he said.
Mr Dasaolu, who is studying accounting and finance at De Montfort University, Leicester, went on: "She never jumped to conclusions. I remember there was a disagreement between a student and another student. Usually most teachers would pick a side or say 'You're both in detention'. But she listened to them and discussed the situation."
He added: "She was a teacher that was loved by everybody. You didn't have to be a good student to love her."
