A 14-year-old fled from the school building after the incident at Dixons Kings Academy, starting a huge police hunt.
The 50-year-old teacher was said to have been stabbed with a knife smuggled into school.
The teacher was taken to hospital with a single stab wound to the stomach. He is said to be in a stable condition and his injury is not believed to be life-threatening.
Detective Superintendent Simon Atkinson, of West Yorkshire Police said: “We have just arrested a 14-year-old male in connection with this offence and he is currently in custody on suspicion of attempted murder.”
The boy was arrested in Bradford city centre.
The victim has been named locally as science teacher Vincent Uzomah, from Leeds.
At Mr Uzomah’s family home, where he lives with his wife Uduak Imeh-Uzomah, the curtains were drawn upstairs and downstairs.
A next door neighbour said: “He’s a really lovely neighbour, a lovely guy. I know Vincent and his wife. I speak to them in the garden. “I know that Vincent is a teacher and he has worked at a school in Bradford in the past. I know this because we have spoken about how naughty the children were there.
“I believe he has taught at different schools and I’m not sure where he is teaching at the moment.”
A woman who lives on the same street and believes Vincent has children, said: “I have heard what has happened at the school in Bradford and I think it is awful. I hope they catch the boy and that he realises there are consequences to his actions.
“I saw Vincent leave this morning as I have been outside all day decorating.
“I often see him and his wife and children and they are all very friendly.
“I know that he is a teacher and I think he teaches all over.”
Khizar Bahadur who is in the same year at school as the arrested schoolboy added: “I’m shocked but I’m not surprised.
“I felt perfectly safe in school today. We were told to stay in our classrooms until further notice until about 11.30.
“All the lessons carried on as planned.
“It’s the first time anything like this has happened. Normally I feel safe. It’s a great school. It was just frustrating to be stuck inside all day.”
Det Supt Atkinson said: “At around 8.55am today, police were contacted by the ambulance service who were attending a report of a member of staff having been stabbed at Dixons Kings Academy in Bradford.
“The male teacher, aged 50, suffered a single stab wound to his stomach and was taken to hospital.
“His injuries are not believed to be life-threatening and his condition is currently described as stable.
“His family are with him at his bedside.
“There were a number of pupils who witnessed this incident, which took place in a classroom, and they are currently liaising with our specially trained officers who are obviously supporting them at this difficult time.
“This is believed to be an isolated incident and the police are continuing inquiries to establish the facts.
“I would like to reassure residents and staff that all necessary resources are being deployed to investigate this ongoing and clearly serious incident.”
Speaking outside the school gates, executive principal Nick Weller said: “It happened right at the beginning of the school day and there were some students who witnessed it. A few students witnessed it - in a classroom.
“Those students have been interviewed by the police.”
Asked if he knew where the teacher had been knifed, he said: “I think in the stomach area. We have a member of staff at the hospital.”
Mr Weller said there was “no internal bleeding” to the 50-year-old victim. His condition is described as stable.
The suspect was described as Asian, with short dark hair, and was wearing a blue uniform blazer.
Mr Weller said there was nothing in school that suggested the attack was going to be launched.
He said: “There was nothing in school that led up to it - there may have been other people outside the school who maybe knew something.”
Mr Weller said a member of staff is at the hospital with the teacher while counsellors are on site supporting pupils.
He confirmed the suspect is a pupil at the school and had been there a year.
Parents arrived at the school - which is next to the city’s ambulance station - to check if their children were OK.
Tahir Jamil emerged saying he had been reassured that his 15-year-old daughter was safe and meeting staff with around four other families.
“They’ve explained everything to us now,” he said.
“Two of the teachers came out and explained everything to us.
“They didn’t tell us what teacher it was but now I’m satisfied. I wanted to take my daughter with me but they assured us that the school is safe.”
Shakeel Ahmed, 39, said he got a text from his 14-year-old son saying there had been a stabbing.
He said he had come to school to see the teenager but police would not let him.
“My son texted my wife and said ‘child stabbed teacher’ - that’s it,” said Mr Ahmed.
“He then sent a text to say everybody’s all right.
“He’s still in lessons.”
Mr Ahmed said: “I came to see my son and see if he’s all right but the police wouldn’t let me in.
“The teachers said he’s OK.”
He said the school was “good” and did not have discipline problems.
But he said: “They should check every child who goes in to check they’re not carrying anything. The school should take its responsibilities.”
Asked how he felt receiving the text, Mr Ahmed said: “I was scared. I didn’t know what was going to happen.”
He added: “The school is good but they should have let the children go home.”
A number of uniformed police officers could be seen coming in and out of the school, which is about a mile-and-a-half from the city centre.
Neil Miley, the school’s principal, said: “Staff were called very quickly and paramedics were called immediately into the school.”
Asked why they kept the school open, he said: “Because I think it’s important that we make sure there’s consistency for our students, as students need to be safe and secure.
“And there’s support from staff on site, making sure our students are looked after, and they’ve responded with fantastic maturity.”
Education Secretary Nicky Morgan said violence of any kind in schools is “totally unacceptable”, adding that her department is “ready and prepared to offer all necessary support”.
Detective Superintendent Simon Atkinson, of West Yorkshire Police, said: “We are conducting inquiries in the area to locate a suspect and I would like to reassure residents and staff that all necessary resources are being deployed to investigate this ongoing and clearly very serious incident.
“We would like to hear from anyone who witnessed the incident or knows the whereabouts of the suspect.
“At this stage we do not believe there is an ongoing risk to pupils or staff at the school.”
A swarm of police cars and vans surrounded the school gates this morning, as concerned parents arrived, trying to find out more about the safety of their children.
A policeman with a dog was seen searching waste ground next door to the school at around 11.30am.
Councillor David Green, leader of Bradford Council, said: “The stabbing of a teacher at Dixons Kings Academy has deeply shocked and traumatised students, school colleagues and the wider community. Our thoughts are with them and the teacher’s family and friends.
“Our first priority, working with the school and the police, was to make sure all the students in the school were safe. We immediately provided specialist support to the school staff and students, and this support will continue over the coming days and weeks.”
Bradford South MP Judith Cummins said: “The stabbing of a teacher at Dixons Kings Academy is deeply shocking.
“Clearly, one incident like this is one too many. Thankfully, incidents such as these are rare. But we mustn’t be complacent. I will be meeting with the school and police as a matter of urgency as the safety of both staff and pupils is absolutely paramount.”
Ian Murch, of the National Union of Teachers (NUT) Bradford branch, which has members at the school, said: “Obviously people are shocked - they would be when an incident like this happens at a school. We hope it can be resolved without any more suffering or difficulties for anybody.”
He said the incident “does raise questions with people about safety and what can be done to improve safety”.
But Mr Murch also said that attacks remain relatively rare compared with somewhere like the United States in terms of incidents in schools, adding: “We have to hope it stays that way.”
The Kings Science Academy was one of the first 24 free schools to open in the country in 2011 and was visited and praised by Prime Minister David Cameron the following year.
However in early 2013 its first Ofsted inspection found that it required improvement. Later that year it became engulfed in scandal after a Department for Education audit report was leaked which contained allegations of fraud. A West Yorkshire Police investigation was launched and three former members of staff have since been charged and await trial, including the school’s founder and former principal Sajid Raza. In January of this year Dixons - an established academy chain in Bradford - took over as lead sponsor of the school resulting in it changing its name to Dixons Kings.