It happened at Thorpe St Andrew School, on the edge of Norwich, at around 10.20am on Wednesday.

Armed police officers swarmed the school and students were told to hide under their desks, with teachers barricading the doors.

Police were called at around 10.20am (Image: Denise Bradley)

A 15-year-old white British boy, believed to be a student at the school, was arrested around an hour later.

He was taken to Wymondham Police Investigation Centre and remains in custody, after detectives were given an extra 12 hours to question him.

The victim was taken to hospital with minor injuries and has since been discharged.

Thorpe St Andrew School reopened on Thursday morning, and a spokesman has now spoken to wish the victim well and praise staff and students for their conduct.

Police arrested a boy around an hour later (Image: Newsquest)

“We have written to families to thank them for the many supportive messages we have received over the past day," he said.

"We are also very pleased to share some reassuring news that the student who was injured has been released from hospital.

"We understand she is doing well and wish her a quick recovery.

"We look forward to welcoming her back to school when she is ready.

“We want to recognise how well our staff and students responded during the lockdown.

"Throughout a prolonged and understandably distressing situation, staff remained calm, focusing on supporting and protecting the students in their care, who in turn showed great maturity and composure. 

The school has thanked staff and students (Image: Denise Bradley)

"As the situation unfolded, staff needed to respond to the needs of the particular students in front of them and adapt their approach accordingly, always with the priority of keeping everyone safe and supported.

"We understand how worrying this event was for families and want to thank our students who coped so well.

"We have shared a range of support measures we are providing for students, families and the community for as long as it is needed. 

“We sincerely hope that we, and indeed every other school across the country, never have to put these protocols into practice again and would like to thank the emergency services for their expertise and response.”

© Eastern Daily Press