They were taken on Pound Lane, just metres from the site, by a woman who was walking her dog.

The woman, who asked not to be named, said: "I was just walking the dog along my normal route and just came across the scene.

A dog walker spotted armed police arresting the suspect (Image: Supplied)

"I had heard there was something going on at the school but wasn't expecting to see anything.

"The boy was standing up on the other side of the police car, with police around him.

"While I was there, about six more police cars came bombing up the road with sirens and lights on.

"He was wearing what looked like a black sweatshirt. He didn't seem to be wearing the Thorpe St Andrew uniform.

Armed police officers swarmed Laundry lane (Image: Supplied)

"He had mousey blond hair and an average build and was white.

"There was no kerfuffle and there didn't seem to be any noise.

"He was then put in the police car and the police cordon was extended to take in this area.

"I couldn't hear anything from where I was standing."

She added that she also couldn't see any blood on his clothes.

"Six more police cars came bombing up the road with sirens and lights on" (Image: Supplied)

Norfolk Constabulary confirmed that a 16-year-old boy was arrested on suspicion of causing grievous bodily harm with intent.

It is understood that the suspect jumped over the school fence at the south site entrance in Laundry Lane after stabbing a pupil, a teenage girl, at around 10.20am on Wednesday.

He has been taken to Wymondham Police Investigation Centre for questioning.

The victim has been taken to the hospital with "minor injuries".

The school was plunged into lockdown for several hours, with students barricaded into classrooms and hiding under desks while police officers stormed the school.

© Eastern Daily Press