The boy had been in trouble for disrupting classes nine times before he was attacked by science teacher Peter Harvey at All Saints' Roman Catholic School in Mansfield, Nottinghamshire, the court was told.
He suffered a fractured skull after the 50-year-old allegedly bludgeoned him with a 3kg dumbbell after his lesson descended into "uproar".
Today, Rex Tedd QC, defending, accused the boy of being a "leading light" behind trouble in the classroom on July 8 of last year.
Nottingham Crown Court heard that the last thing the boy remembered was swearing at Harvey, who replied: "I'll teach you to f*** off."
A video of the interview the boy gave to police was shown to the court.
In it, the boy, now 15, is slumped on a sofa wearing blue jeans and a black hooded top. The left side of his face was swollen.
He said: "I can remember all the class being noisy and rowdy. They were all messing about and there was a girl messing with the blinds. He stamped at her and told her off.
"She swore at him and walked at him and then some other girls left the class because they felt scared.
"He said something to me and I swore at him. He said, 'I'll teach you' and swore at me.
"I can remember being dragged out of the classroom and into the corridor."
Another boy, now 15, witnessed the attack.
In his police interview he said Harvey acted as if "possessed" when he caught up with the alleged victim.
The witness told police: "He said, 'What are you doing, you stupid boy?'. He told him to 'f-off' and he got him round the neck.
"Mr Harvey went mad. He gets him by the neck and collar and drags him out of the class. He was unusually scary, it wasn't normal.
"It was like something had possessed him, you could see he wanted to kill him, sort of thing. He was dragging him out at such a rate and pulled him across the corridor. He was so angry it was like he had an extra power to do it.
"(He) is a small boy but he isn't weak or feeble, but Mr Harvey was manhandling him out of the door."
Recalling the attack with the dumbbell, the witness added: "He was just striking him with it and was just saying 'die, die, die'. (He) was on his heels leaning back.
"Blood was pouring out of his face. I thought he was dead. His eyes were open and I thought he was dead.
"He (Harvey) came out looking calm, like he hadn't done anything. A teacher had his arm around him."
Earlier the court heard the boy attacked by Harvey had been at the school for three years.
That day he had been typing up his English coursework on a computer before his science lesson with Mr Harvey.
The teacher had planned to do an experiment with the class but due to bad behaviour had asked them to copy out material from text books.
Rex Tedd QC, defending, put it to the victim that he regularly disrupted lessons.
Mr Tedd said: "On nine occasions in the last year you deliberately disrupted the teaching of your class. Can you remember anything about that?"
"No," replied the boy.
"My suggestion is that you were a leading light in the trouble in that took place in that class."
"No," repeated the teenager.
The barrister said: "You're saying you cannot remember any of the trouble that took place in that classroom?"
"No," the boy said.
Mr Tedd also put it to one of the youngsters in the class, who had earlier told how he tried to drag Harvey off the boy, that pupils would secretly film teachers as the youngsters tried to wind them up.
The footage would then be shown around the school to humiliate the teachers, the barrister said.
"The main point of it, what was so amusing, was that the teacher would be provoked into making a fool of himself."
The boy, now 15, replied: "From time to time, that was the point of it."
Judge Michael Stokes QC, the Recorder of Nottingham, asked the same boy: "Can you explain to the jury what's funny about winding up a teacher who has been off ill?"
The boy replied: "There was nothing funny about him. What was funny was we were just having a good time with our friends."
Yesterday, the jury was told Harvey shouted "die, die, die" as he attacked the boy after his class descended into "uproar".
Moments before the teacher launched his attack, the boy was playing volleyball with screwed-up bits of paper before sword-fighting with metre rulers in a game of "high jinks".
The class was in chaos, with pupils calling the teacher a "psycho" after he threw out one 14-year-old girl who was messing about with the window blinds.
She stormed out crying, calling him a "bald-headed bastard" in front of classmates, the court was told.
One pupil secretly filmed Harvey, deemed a "soft-touch" by students, with a camcorder to "humiliate" him as he tried to regain control of his lesson.
In the video he could be heard shouting at his victim to stop fighting with the wooden ruler, one of many occasions when teenagers would "push the boundaries" in his lessons.
Moments later he grabbed the youngster by the collar and dragged him out of the classroom and into a nearby preparation room on the second floor of the school's science block.
The married father of two then ferociously hit the boy about the head with the 3kg (6.6lb) weight, leaving him unconscious with a fractured skull and severe cuts.
Stuart Rafferty QC, prosecuting, told the court: "No one can say for one moment what happened to this boy was deserved or justified.
"What he (Harvey) did was grossly disproportionate to the wrong inflicted on him by the boy or other members of the class. There was simply no excuse for what happened."
Following the outburst, Harvey was taken into custody where he told police that during the attack he felt like he was watching himself on television. He said he was not feeling any emotion and "couldn't think at all".
Earlier, the jury was told Harvey had a history of mental health problems. He could often be heard talking to himself and could be aggressive towards students.
A teacher at the school for 16 years, he had been sent home in December 2008 by its education adviser Shahrukh Mugaseth after he admitted having thoughts of harming someone.
But he returned to work in April last year after receiving counselling sessions from a therapist who told him he was too "peaceful and passive" and needed to be better at letting his anger out.
Harvey had also been off after a pupil threatened him at his home after he stuck up for a female colleague who had been pushed into a bush, while on another occasion he was left stressed out after a disruptive student was moved to his class.
One 15-year-old girl, who was in the Year 9 class when the attack happened, claimed she confronted Harvey about his behaviour moments before the attack.
In an interview given to police, she said: "I said to him 'Sir, I think you are having a mental breakdown' because people were scared of him. He started murmuring something about killing me."
Describing the attack, the girl added: "He grabbed him by the neck and forced him out into the corridor. The class ran out and he got him to the floor.
"By this time he was doing something to him. He grabbed a weight and hit him on the head constantly. He didn't stop and blood was everywhere. Everyone was screaming and then two people went and got teachers."
Harvey, who appeared in the dock dressed in a beige suit and brown tie, has already admitted one count of causing grievous bodily harm without intent.
But prosecutors are seeking to prove he knew what he was doing when he attacked the boy. They claim it is attempted murder but if the jury reject this, Harvey could be found guilty of an alternative charge of grievous bodily harm with intent.
