At some point, we've all been bystanders - frozen to the spot, gaping as a mugger makes off with a purse, a drunken friend grunts lecherously at a passing woman or a colleague vents casual homophobia in the staffroom.
The Mentors in Violence Prevention (MVP) programme homes in on the bystanders - that overwhelming majority of people more likely to witness an unpleasant incident than to be the perpetrator or victim. Do not think your peripheral involvement allows you to be passive, it warns: bystanders, by their very lack of action, are part of the problem.
It's a bold message, and even more so as those entrusted with delivering it are still in their teens (see pages 12-13). Seven Scottish secondary schools have so far deployed MVP, training senior students to help their peers intervene in and prevent violence. Many more institutions are due to follow.
These students, known as "peer mentors", have a credibility that no teacher can hope to match. They do not cause a room to cringe when they slip into youth slang; they reference current music and films without having to crib notes from BBC Radio 1 the night before. And staff place huge trust in the mentors - some schools have even decided that no teacher needs to sit in on the sessions. It really is teenagers talking to teenagers.
Just as well, given that mentors, who tend to work only with peers of their own sex, can start their first session with a "gender box" activity. For example, male mentors ask boys to write on a piece of paper words that sum up what it is to be - and not to be - a man.
Even with guaranteed anonymity, one wonders if the boys would be so frank if a teacher was going to peruse the box's contents. One mentor told us that real men had been described as "strong", "macho" and "womanisers". Men who did not cut the mustard were "pussies", "poofs" and "gay".
Another mentor, a highly articulate 17-year-old girl, told us that, before getting involved with MVP, she thought it was normal for some boys to be controlling in a relationship.
A male mentor told us that "sexting" - using smartphones to send explicit pictures to a love interest - was common among teenage couples, almost expected. The prospect that spurned (or merely unkind) boyfriends might then forward the images to all and sundry was often trumped by girls' fears of looking prudish.
MVP tackles violence in the broadest sense, from physical thuggery to online humiliation. In all its forms, violence is supported by a bedrock of prejudice, stereotypes and myths. These need to be excavated and exposed as the nonsense they are.
Teachers can do some of the groundwork, but MVP shows that help from students may be invaluable.