It was her day off, but teacher Ann Maguire, 61, still insisted on going to college to help students prepare for the exams.
She was at the Corpus Christi Catholic College in Leeds, England, for just 45 minutes, when a boy allegedly walked up behind her and repeatedly plunged a knife into her neck and back, Mail Online reported.
It was a rare attack on teachers in England, and it triggered nationwide sympathy.
Mrs Maguire - described as "simply the best" by students - died in "a truly shocking and appalling tragedy", British Prime Minister David Cameron said yesterday.
As she was being stabbed on Monday, she begged students to flee the classroom, rather than see the horrific attack by a fellow student.
Mrs Maguire had earlier told her husband, Don, 62, that she could not spend the day with him at home because she wanted to help students prepare for their exams.
The popular Spanish teacher was also in her last term before retiring from full-time work at the school, where she spent her entire 40-year career.
One teenager said: "Mrs Maguire was screaming at the kids in the class, telling them to get out because she didn't want them to see what was happening."
It is understood that the boy, described as a depressed recluse who chose to sit alone in class, chased her from one room to another before she collapsed in the arms of another teacher.
Witnesses said the teenager then dropped the knife and fled the room smiling, before being tackled by the school's assistant head teacher.
Detectives asked for more time to question a 15-year-old boy over the murder, and said the suspect has been treated for a minor hand injury.
The class of 30 teenagers saw the stabbing and many of them stayed at home with their families on Tuesday.
"There were a number of stab wounds to the lady in question," said Chief Superintendent Paul Money of West Yorkshire Police.
RISING SCHOOL VIOLENCE
Violence in British schools has risen in recent years, and there has been growing concern over knife attacks involving teenagers, AFP reported.
But fatal attacks on teachers are extremely rare.
Mrs Maguire's death is believed to be the first of its kind since 1995, when London headmaster Philip Lawrence was stabbed to death outside the gates of his school as he went to help a pupil.
This article was published on May 1 in The New Paper.
Get The New Paper for more stories.