A TEACHER was engulfed in thick black smoke after she was trapped in her office by a pupil.

The 16-year-old, who cannot be named, was alleged to have set fire to a chair outside the year-head's office, trapping her inside.

He was said to have bragged to pupils about how he started the fire, but now denies arson with intent to endanger life.

Newcastle Crown Court heard how 1,300 pupils were inside the County Durham school building when the fire was started.

Staff and pupils escaped unscathed, but the court heard how the teacher was left frightened and upset.

Graham Duff, prosecuting, told the jury how the teacher was in the middle of a telephone call when she noticed smoke billowing round her door. "She was in a dilemma, she thought if she opened the door there might be flames but could not get out through the window," he said.

"She decided to open the door slightly and she was immediately engulfed in thick, black smoke.

"She turned acutely right and trailed her hand along the wall towards a class room where she managed to get out."

The fire caused £24,000 damage to classrooms and corridors in the Catholic school.

The court heard how the pupil was caught on security television, lingering around the area of the fire, at about the time it started.

The case continues.