A teenager has been sentenced to six years in a young offenders' institute for attacking two teachers, one of whom was shot with a 950,000-volt stun gun.
The attack took place outside the school gates
Marvin Airey, 19, from Redcatch Road, Bristol, temporarily paralysed maths teacher Peter Kelly outside Ashton Park School in Bristol last October.
He also punched a female teacher, who fractured her skull in the attack.
Bristol Crown Court heard Airey, a drug user with many previous convictions, bought the stun gun over the internet.
Jonathan Stanniland, prosecuting, said Mr Kelly had been patrolling the playground when he spotted a black Vauxhall Corsa parked near the school fence.
Airey got out of the car and confronted the maths teacher.
He said Mr Kelly "felt a sharp pain and thought he had been stabbed".
Airey then launched a savage attack on supply teacher Mollie Dawnay who rushed to Mr Kelly's aid.
Mr Stanniland said: "He struck her with one hard blow into her jaw area."
The prosecutor added that Mrs Dawnay "appeared to be unconscious before she hit the floor".
Airey fled the scene and the emergency services were called to help the injured teachers.
Mrs Dawnay suffered a fractured skull in the attack and has only recently been able to return to teaching.
Airey previously pleaded guilty to a charge of grievous bodily harm, possession of a prohibited weapon and common assault.
Defence lawyer Ramin Pakrooh confirmed that the stun gun was capable of discharging up to 950,000-volts.
He said Airey had a troubled childhood and became involved in drugs around the time of the attack.
Judge John Foley said: "It was an example of appalling gratuitous violence of the very worst type."
Det Con Adam Stacey from Avon and Somerset Police, who worked on the case, described Airey as a violent man.
Speaking outside court, he said: "It was a sudden unprovoked attack of extreme cowardice.
"I'm pleased to see a violent man behind bars where he should be."