The teenager, who cannot be named because of his age, admitted to the attack earlier this month, just weeks after stabbing Jamie Sansom at Tewkesbury Academy on 10 July.

The academy was locked down and two neighbouring schools were also asked to shut their doors as a "precaution" after the stabbing happened.

Mr Sansom, who has taught maths at the Gloucestershire school since 2017, was taken to hospital and discharged the same day.

He has said he is "recovering well".

Bristol Magistrates' Court heard the youth had put on a snood and a hooded top to cover his face and taken a six-inch kitchen knife from his home.

Before confronting Mr Sansom he had told a friend to "wait until period one" and minutes before the attack dialled 999 to inform them a teacher would be stabbed.

On 4 September, the boy admitted to one charge of attempting to cause grievous bodily harm with intent, having previously pleaded guilty to possessing a bladed article.

He has been held in custody since being charged.

Imposing a 14-month detention and training order, District Judge Lynne Matthews told him: "You were not acting impulsively.

"You took the face covering to school, you took the knife to school.

"You told a friend what was going to happen and you told the emergency services.

"Nothing strikes me about it that was impulsive."

The judge said he would serve half the sentence in custody with the remainder at home working with the youth offending team.