A 16-year-old boy accused of the attempted murder of a teenage girl who was stabbed at a secondary school has admitted having a blade without lawful authority.

Armed police were scrambled to Thorpe St Andrew High School, on the outskirts of Norwich in Norfolk, in March following reports that a 15-year-old girl had been stabbed in the back.

The school was placed in lockdown for almost three hours and teachers are said to have barricaded classroom doors, while scores of anxious parents waited outside.

The alleged victim was taken to hospital after the incident and was said to be ‘doing well’ when she was discharged the following day.

The young defendant, who can’t be named for legal reasons, appeared via video link at Norwich Crown Court today, where he pleaded not guilty to attempted murder but admitted having a kitchen knife without lawful authority.

The boy, who remains remanded in custody at a youth detention centre, is due to face trial at the court on October 5.

A previous hearing at Norwich Magistrates Court was told that the school went into lockdown on March 11 after a number of 999 calls were made.

Prosecutor Josephine Jones told a district judge: ‘CCTV of the toilet area shows a male all in black wearing a black mask' carrying a 'carving knife with a lengthy blade'.

She added: 'The victim had been stabbed to the back.'

Ms Jones said the defendant is claimed to have fled but was arrested by police nearby.

The boy's father sat on a chair outside the secure dock, close to his son, as he listened to proceedings in March.

The parent wiped tears from his eyes at the end of the hearing, having been offered a box of tissues.

Police were called to Thorpe St Andrew School at 10.24am on the day of the alleged attack.

The girl, who also can't be named, was described as 'doing well' when she was released from hospital.

Thorpe St Andrew School said in a statement at the time that staff 'remained calm' throughout 'a prolonged and understandably distressing situation'.

A spokesman said: 'We have written to families to thank them for the many supportive messages we have received over the past day.

'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.

'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.'

The school added that they 'understand how worrying this event was for families' and that a number of support measures will be provided to students and families for 'as long as it is needed'.

The statement continued: '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 yesterday.'

Around 100 parents arrived at the school grounds after hearing the reports on social media and stood outside pleading for information.

Teachers are understood to have used items such as cabinets to barricade classroom doors with the school under lockdown for almost three hours.

A case management hearing is due to take place at the crown court on September 1.