A colleague, who had come to check what was happening, described Williams' screams as "gut-wrenching".

The police and emergency services were called and the school was placed in temporary lockdown and was closed the following day.

Williams suffered several injuries, including a 7cm (2.8 in) wound to her lower back, and was taken to Withybush Hospital in Haverfordwest.

The boy was later arrested at his grandmother's house.

Rees said the prosecution's case was that the incident was "a deliberate act to kill", while the defence would argue it was an accident.

The jury watched an interview that Williams gave to police on the night of the incident in which she said the pupil was "trying to kill" her.

"I thought I was dying, I thought I was going to bleed out, I thought I had seen my daughter for the last time," she said.

She explained how he came to her classroom "cool and collected" at the end of the school day to ask if his "work was correct".

She said that "got [her] confused" because he had "never seemed bothered before".

"I had never had a cross word with [him]. He's a low ability child but he's got on with his work in class," she said.

"I've never had anything bad to say."

Williams said he was trying to "keep her talking" while he went to close the classroom door because it "was cold".

"He was trying to subtly get behind me," she said, "which felt weird".

"He kept on trying to come back to the work and, all the while, he was trying to find something in his bag," she added.

"I ask him again, 'are you sure you're alright?' And then he pulls [the knife] out of the bag and lunges at me.

"I felt it on my head. I thought to myself, 'I hope that isn't a knife because I'm dead'.

"He pulled it back and I could see it was the pointy side. I managed to grab the knife, hence my cuts, he was trying to get it to me again.

"He pushed me back in to my chair, I'm screaming, I'm shouting. I managed to push him and I'm left holding the knife. He runs out."

She said he "did not say a word" when he "lunged" at her.

"He was eerily quiet," she said.

"His mouth was straight. His eyes, I've never seen anything like it. The look in his face was pure hatred."

Williams said she shouted at colleagues for help in panic, as the boy ran away.

She said: "I always thought we had a good relationship, that's what's upset me the most, is I have no idea where this came from."

The trial continues.