The message was sent out by Thorpe St Andrew School at 9.27am on Wednesday.

At 10.25am, shortly before break time, the school went into lockdown after the girl was stabbed.

The incident is understood to have taken place in the maths block, in or near the toilets.

The 15-year-old student was arrested around an hour after the incident (Image: Newsquest)

Armed police were sent to the scene and conducted searches of the campus and surrounding area before arresting a suspect, a 15-year-old boy on a nearby street.

The message to parents was requiring them to check their emergency contact details and ensure they were up to date.

It is not known if the request was prompted by specific security concerns the school was aware of or if there was any kind of link to the incident.

The school have been approached about the timing of the pre-incident email.

Parents were told to check their contact details around an hour before the incident unfolded (Image: Newsquest)

Norfolk County Council, which provides support for the region’s schools, said it had no involvement in the message.

The email said: “It is essential that we have the correct details so that we can contact you quickly in the event of an emergency and ensure that important school communications can reach you without delay."

The message, which asked parents to update their details on Arbor, an information management system, was the last communication parents received from the school for nearly four hours.

The next email, sent at 1.15pm, told families that the lockdown was ending and pupils could leave the site.

In the intervening period, while children hid under desks and teachers barricaded classroom doors, more than a hundred parents gathered at the school gates.

Parents waited anxiously to hear about their children at Thorpe St Andrews School. (Image: Denise Bradley)

With no word from the school, they pieced together what was happening through media reports, police updates and messages from their children.

The lack of communication from the school caused frustration for many parents.

It is understood the school shut down its internet connection as part of its emergency procedure to prevent rumours spreading among pupils.

Some students' phones are also believed to have been confiscated during the lockdown.

The decision to lift the lockdown was taken jointly by police and the school's headteacher, Penny Bignell, who later described the day as "incredibly traumatic".

Headteacher Penny Bignell described the day as "incredibly traumatic."  (Image: Newsquest)

The school sent out a more extensive update to parents that evening.

The victim of the attack was taken to hospital with what police described as minor injuries.

The 15-year-old boy, identified by police as white British, remains in custody at Wymondham Police Investigation Centre.

Norfolk Constabulary confirmed the attack is not linked to a separate incident last week in which a pupils from visiting Jewish school said they were subjected to antisemitic abuse during a football match.

The Thorpe school has since reopened, with parents given the option of deciding when their child returns.

© Eastern Daily Press