A teenager has been arrested on suspicion of attempted murder after a teacher was stabbed in front of pupils in a classroom, police said.
The 14-year-old boy allegedly attacked the male teacher - named locally as science teacher Vincent Uzomah, from Leeds - with a knife smuggled into school.
The 50-year-old teacher at Dixons Kings Academy in Lidget Green, Bradford, 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.
Det Supt Atkinson went on: "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."
Det Supt Atkinson was speaking in front of the school, which is about a mile and a half from the centre of Bradford, shortly after hundreds of pupils left for the day.
He said specialist trained staff were talking to the children who witnessed what happened.
"We're speaking with the pupils there to see what they actually saw," Mr Atkinson said.
"We've got a welfare issue to make sure we manage as well since they potentially witnessed something horrendous."
The detective would not comment on whether police had recovered a knife or what help staff and pupils gave to the injured teacher. But he said the incident happened in a science class.
Superintendent Damien Miller said he wanted to offer his assurance to the people of Lidget Green, which he described as a close knit-community.
Supt Miller said: "Lidget Green is a close knit community and we would like to offer our assurances. There have been increased patrols in the area, and we have been working with pupils, staff at the school and the wider community, and most importantly, the victim and his family.
"We would like to reassure the community that officers will stay in the area and work with the school and partners in the weeks ahead. Our thoughts are with the teacher in hospital."
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