The mother of a teenage boy who stabbed a girl in a masked attack at a school said she received a message from her son saying “sorry” shortly after the attack, a trial has heard.

Police were called to Thorpe St Andrew School, near Norwich, on 11 March following reports a 15-year-old had been stabbed in the back.

The defendant, who is 16 and cannot be named for legal reasons, denies attempted murder, but has admitted possessing a kitchen knife without lawful authority and wounding with intent.

After learning about the unfolding events on social media, his mother told the jury at King’s Lynn Crown Court she “was in complete shock” when she realised her son was involved.

The mother told the trial that her son was “very quiet, very funny, very smart” and had a “dry sense of humour”.

The court has previously heard how the defendant had written notes saying he hated women while the schoolgirl victim described to police how she told a teacher “Sir, I’ve been stabbed”.

During Monday’s proceedings, the mother described the night before the attack as “completely normal”, and said her son left for school at his usual time the following morning.

She said she first became aware something was happening when she was “doom-scrolling”.

She messaged her son asking if he was OK, but said she did not “get an immediate response”.

“When you realise there has been an incident at the school and you don’t hear from children, it’s worrying,” she said.

She had the ability to see her son’s location using a phone app, and messages on social media had said there had been a knife attack and that someone had left the school grounds.

“When I saw he wasn’t at school and someone had run away I was concerned [my son] was involved,” she told the court.

She said she received a message on her phone saying “I’m sorry”, and when she called her son and asked what had happened, he replied “nothing good” and that he had “hurt someone”.

She told the court her son did not sound like himself, spoke in “very short sentences” and “sounded very upset”.

Alongside her husband, she went to try to find her son and was passed by two police cars “with blues and twos on”.

She called 999, gave the police her son’s location, and was advised to head home.

“I was in complete shock,” she told the court.

Prosecuting counsel Christopher Paxton, KC, asked the mother if there were any concerns about how her son was using his phone and if she was checking his phone.

She answered “no” to both questions.

A teacher who chased the boy following the attack described how the then 15-year-old had “legged it”.

He told the court that a person who witnessed the stabbing came to him and said “she’s been stabbed”.

When he went to the corridor, the teacher said “the only person I saw was dressed completely in black”.

He said he was “very shocked” and shouted to the boy to stop.

He told jurors he ran after the boy for about 25 seconds and continued to shout “stop” and saw that a black glove had been dropped.

The trial continues.

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