Teen stabbings are rarely out of the headlines. But a course which answers such questions as why even a cut to the buttocks can kill aims to stop pupils carrying knives.
When the bell rings at the end of a lesson, usually all that remains is the odd textbook and a lingering smell of sweaty sports kit.
But trainers confronting pupils with the dangers of weapons in schools are collecting something much more sinister - knives.
At the end of each Be Safe weapons awareness course, pupils are asked if they would like to hand in their blades, or leave knives under their seats.
Hundreds have been left behind at the courses which have been running mainly in London and surrounding counties since 1998. The Be Safe project also teaches people to run the courses, and there are now 330 trainers working nationally with young offenders and in schools.
And a new campaign - No To Knives, backed by the Royal Armouries Museum - hopes to help make more courses available across the UK now knife crime is on the rise.
NO TO KNIVES
Launched by Royal Armouries Museum on Thursday
Wants one million pledges not to carry knives
Message is there are better ways to stay safe
Be Safe organiser David Morris says: "If we are working in a school - an inner city school anywhere in the country - around a third of a class of 30 pupils will put up their hand and say they have carried a knife at some point."
But few grasp the implications of using one. Mr Morris, a former police officer, says young people tend not to think beyond putting the knife in their pocket or bag.
"Most say they are carrying it for self-defence, but [their] knife has never been used for this and never will be."
During the lesson the trainers set out to debunk the pupils' misconceptions about carrying knives. First up is there's no such thing as a "safe stabbing".
"Some say you can stab someone on a safe target, such as arm, leg or buttocks. Areas you can stab and it won't kill them, which is blatantly untrue as you can, you can still kill them like that," says Mr Morris.
Pupils are shown photos of what a knife can do to the body
Few know what they would do if actually confronted, instead hoping that pulling out a knife will simply scare people off.
"So we give them real-life case studies where someone pulled a knife, didn't want to use it, the person jumped them, pulled a knife on them and killed them."
What makes the pupils sit up and take notice is when he talks about the number of American police officers killed with their own weapons - officers who have been trained how to retain their weapons when confronted.
Why don't they think this will happen to them? "A lot of them talk about stabbing people. They are so blase about it, a lot of it is bravado," Mr Morris says.
Eye for an eye
He adds that young people often forget that friends and family are victims too when someone is stabbed - and that some of these people may feel a need for revenge.
To ram this point home, Ann Oakes-Odger, whose son Westley was killed with a knife at a cash machine, is often invited to speak to the pupils.
"She speaks so eloquently about what it is like to be a mum and lose your son. All of these kids love their mums, so it gives them a different perspective."
At the end of the course, some have been persuaded to give up weapons.
"These kids are sitting down, listening to the facts and making a choice. You sow the seeds in their minds and get them thinking," says Mr Morris.
"You hope in your heart of hearts that some of them, when faced with the choice of picking up a knife, are going to change their minds."
Here is a selection of your comments.
Young people today don't understand knives at all - they quite often never eat with one, or learn about them as I did forty years ago, by having a penknife and cutting/whittling wood, fingers, conkers etc. I was amazed when taking some 16 yearolds sailing recently how inept they were when a sharp instrument was involved.
Tim Hughes, Oakengates
This is a start, preventing even one of these kids stabbing someone is a win, but more needs to be done, the laws must change and punish those severely caught with knives. In Australia you are not even allowed to carry a butter knife around, and if caught face harsh penalties.
Anthony R, London , UK