Students continue to pay tribute to their teacher Anne Maguire, who died after she was repeatedly stabbed in her classroom in front of her pupils in Leeds.
A 15-year-old boy remains in custody tonight following the death of the Spanish teacher at Corpus Christi Catholic College on Monday morning.
Mrs Maguire's death, after more than 40 years teaching at the school, is thought to be the first time a teacher has been stabbed to death in British classroom, and the first killing of a teacher in a school since the 1996 Dunblane massacre.
Children leaving the school this afternoon said the teacher was attacked as she taught a routine year 11 Spanish class in the Modern Languages block of the school.
Some pupils reported hearing screams as other members of staff rushed to the scene and restrained her attacker.
Tonight, hundreds of pupils, former students and their parents crammed into the pews of the Corpus Christi Church, next to the school.
There was no formal service but teenagers hugged each and some lit candles as they wiped away tears.
A few yards outside, scores more youngsters gathered around hundreds of floral tributes which have been placed at the school gates.
Some teenagers pinned photographs to the railings, along with teddies and other memorabilia.
All of the youngsters described Mrs Maguire as a inspirational teacher who went out of her way to help students.
She had taught at the school since she was a student teacher and, last year, celebrated 40 years at Corpus Christi.
Prime Minister David Cameron led the tributes tonight. He said: "This is a profoundly shocking, indeed absolutely appalling, incident.
"All our thoughts are with the teacher's family, with the school and all the pupils who study there. Everything that can be done to help this school get to the bottom of what happened will be done. I think that we have to wait for the investigation to see what exactly happened."
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Teacher stabbed in Leeds
Katie Gallagher, 15, said she was in a nearby room when Mrs Maguire was stabbed.
She said: "I heard her scream. I was in a meeting at the time but I heard it."
She said everyone in her class burst into tears when they were told about the teacher's death.
Former pupil 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 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: "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.
"She was just lovely. She was wonderful. I am devastated."
Nichola Davies, 34, broke down as she tried to explain why she had driven 40 miles from Goole, East Yorkshire, 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."
One of the notes left with the flowers said: "You inspired countless generations. You taught four generations of our family and you were simply a totally fantastic teacher, always caring and always there to make us smile (even if you were speaking Spanish)."
Mrs Maguire, who lived in the Moortown area of Leeds with her husband, Donald, is understand to have two grown-up daughters.
She was head of year 11 at the school for more than 10 years.
There are nearly 1,000 pupils on the roll at Corpus Christ, aged between 11 and 16, according to the school's website.
Parents outside the school tonight said it had a very good reputation and, despite being located in a challenging area, families competed to send their children there.
Speaking outside the school earlier, Chief Superintendant Paul Money, from West Yorkshire Police, 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."
He said he could not confirm what injuries the teacher had received following reports she was attacked from behind and stabbed in the neck and back.
Dean Sean Quigley, from Corpus Christ Catholic Church, said: "She was just a wonderful, caring person. She was head of year 11 for in excess of 10 years and she was just so patient in her pastoral work.
"She was held in such immense esteem. She taught the grandparents of some of these children here today."