David Cameron has paid tribute during Prime Minister's Questions to Ann Maguire, the teacher stabbed to death in a classroom, calling it a "truly shocking and appalling tragedy".
The Prime Minister told MPs: "It is clear from the tributes paid she was a much-loved teacher who'd worked at the school for over 40 years.
"She cared so much about her pupils she'd come in on her day off to help prepare them for exams."
Police have been given extra time to question a 15-year-old boy over the incident.
Although a shocking attack, this is a rare attack. There are few other occasions when a teacher was stabbed inside their school by a pupil.
A 15-year-old schoolboy is in police custody tonight, suspected of stabbing to death his teacher.