Thorpe St Andrew School, near Norwich, was plunged into lockdown after the pupil was attacked at around 10.20am on Wednesday.

Children were told to hide under desks and the school bell could be heard ringing out across the site.

An officer inside a classroom (Image: Supplied)

It is understood that teachers told pupils not to go on their phones at the time but, after around an hour, they were allowed to start messaging their families.

At 11.34am, police announced that the suspect was on the run and that the victim had suffered "minor injuries" as a result of the attack.

Police cars parked outside the school gates (Image: Newsquest)

It is understood that the suspect jumped over the school fence at the south site entrance in Laundry Lane when fleeing the scene.

A 16-year-old boy has been arrested on suspicion of causing grievous bodily harm with intent just before midday and taken to Wymondham Police Investigation Centre for questioning.

Children have now been sent home, with one student at the school gates describing the incident as "really scary".

Police outside Thorpe St Andrew School (Image: Newsquest)

They said that, in one Year Seven class, the teacher barricaded the door using a cabinet.

Another said they saw a girl "covered in blood" and worried pupils were texting between classrooms.

Other parents have shared the worried texts their children sent them during the ordeal.

One simply read: "I am very scared".

Another pupil said that they "just want to go home".

Armed police outside Thorpe St Andrew School (Image: Newsquest)

Children have since been allowed to leave the school and a cordon remains in place at the Year 11 entrance of the school.

A statement from Broad Horizons Education Trust, which runs Thorpe St Andrew School, said: "We have clear procedures in place and our staff acted swiftly, with the whole school going into lockdown with children staying in their classroom with their teacher.

"One of our students was injured and is now being treated in hospital for minor injuries.

"This has obviously been a distressing experience for our whole community and our focus now is on making sure all students feel supported as we begin to understand what happened."

© Eastern Daily Press