It's lunchtime at an Illinois elementary school and the decibels are rising as children finish off their food. Suddenly, a flashing yellow light in the middle of the room switches to red. Without so much as a blown whistle or a bark from a teacher, the students fall silent.
This is the controversial Talk Light system in action at the JB Nelson school in Batavia, 30 miles west of Chicago, where teachers are trying an alternative to the traditional behaviour management method of fighting noise with more noise.
There is no verbal intervention from adults. If the volume of the dinner hall rises above 78 decibels (the same level as is generated by heavy traffic) the "traffic light" turns red and the children have to sit in silence for one minute.
Brenda Sand, the school principal, says: "It has really reduced us having to shout at them." She adds that Talk Light has dramatically reduced the antisocial behaviour that comes with increased noise.
I stumbled on the Talk Light system when, as a newly qualified teacher, I was on the internet looking for alternatives to shouting. While this robotic dinner supervisor seems an effective substitute for shouting, the idea of computer-controlled children is unappealing to many of us.
Nevertheless, Talk Light is an indication that some schools are taking seriously the need to stop teachers straining their voices by shouting at children.
Two terms into my first job, I'm wondering when (and if) it's acceptable to shout. I already know there's a gaping void between the theory and practice. Throughout my PGCE training at Goldsmiths, London, the line was to avoid it: proper teachers used non-verbal techniques such as eye contact and gestures. Often, we were told, lowering your voice was more effective.
If you raised your voice, disruptive children would increase their volume to match.
So, don't shout, it doesn't work. But it's not as straightforward as that.
I shout, and it works. I lost my shouting virginity last September when a Year 7 student started throwing disgusting (but impressively imaginative) insults at his classmates. I took him to one side and shouted so loud that he trembled. He's been amiable ever since. Would a more understanding approach have worked better? Perhaps, but I'd tried and it hadn't worked.
At my school a senior member of staff - and one known to have impressive behaviour management - bellows at children regularly. His roar reverberates down the corridor, to be followed soon after by a shell-shocked miscreant.
Rather than registering shock or disgust, passing teachers simply offer each other a playful grin. So certain members of staff use shouting as an option. And they're not bad teachers.
Children themselves aren't as hostile to shouting as I'd previously assumed. I've asked my students, and the majority believe shouting works in small doses, especially when they first encounter a teacher. "The first impression is really important," says Year 11 pupil Kathryn. "If the teacher seems too easygoing you might think they're a pushover and be naughty next time you see them."
Most students can offer an example of a respected teacher who terrified the class at first meeting and never needed to shout at them again. It's important that the dressing down is genuinely scary. "If they don't sound like they mean it, you don't listen," says Lavell, a Year 8 boy. "You just find it funny."
Most teachers have memories they wish were just bad dreams. Lavell's remark reminds me of a disaster from one of my trainee placements when I timidly raised my voice - it was a pathetic semi-shout - at a class of 13-year-olds. They'd given another teacher a nervous breakdown a few months earlier.
"Don't speak to a teacher like that!" I cried. "You're not a teacher!"
chorused Year 9, like young lions ripping into fresh meat on the stuffy savannah.
But, executed credibly or not, is shouting a good idea? Some experts argue that the short, sharp shock that settles many children can harm others. Dr Marion Farmer, senior lecturer in child psychology at the University of Northumbria, is an expert on the 5 per cent of the school population with language development problems (for example, those on the autistic spectrum). "Shouting," she says, "can make kids with autistic spectrum disorders extremely anxious, as anxiety is a major symptom of those disorders."
Siobhan Mellor, an educational psychologist and specialist in children with behavioural difficulties for Kent County Council, isn't a shouting fan either. Ms Mellor has visited schools where "there is a culture of shouting and everyone shouts - teachers and students. It's unproductive and unhelpful. It's easier to do it in a non-verbal way."
While I've seen shouting work, I've also heard the horror stories about teachers' voices. After all, town criers and circus ringmasters have plenty of time to warm up. Sudden, shocking shouting (the type teachers tend to use) is the vocal equivalent of going from reverse gear to 100 miles an hour in a split second.
"If you are listening, you're probably holding your breathing muscles," says Alan Woodhouse, a voice expert who has worked on television soaps such as Holby City. "If you then try to get a lot of volume out quickly, you're putting the larynx through a great deal of stress."
The voice is a strong but sensitive mechanism. When the vocal cords bang together forcefully, a delicate mucus layer can become damaged, leading to nodules and other complications.
Mr Woodhouse offers a sporting analogy. "Jumping straight into shouting is a bit like sitting in an armchair all day eating biscuits then suddenly going for a sprint. It's hardly surprising that you feel red in the face."
Coupled with an emotional surge (faked or otherwise) and the stress of the situation, shouting can make your blood pressure soar. My head of department occasionally resorts to shouting, but he says he always feels odd for the rest of the day.
Like the psychologists, Mr Woodhouse is dubious about its effectiveness.
"We all get angry, we all shout, but we know that by doing this we weaken ourselves," he says. "I teach actors that when a character shouts, that character appears weaker. It's the same in real life."
Once again, the expert theories don't match the reality of my working life.
I don't get a kick out of shouting, and I do it as rarely as possible, but I've learned from experience that it's an effective strategy in managing the behaviour of certain kids and classes. I suspect there are plenty of teachers, NQTs and otherwise, who feel the same way.
Joe Curtis teaches English at St Paul's RC school, London borough of Greenwich: firstname.lastname@example.org. For more information on the Talk Light system, go to www.talklight.com
LOVE THAT LARYNX
Whether we think shouting is a mistake or a useful control strategy, most of us do it sometimes. Here are my tips (with help from voice coach Alan Woodhouse).
* When shouting, I try not to stand with locked knees and a tense stomach, as this forces the voice out uncomfortably.
* Alan Woodhouse says: "If in doubt, breathe out." You "take the brake off" your voice by breathing out, and can then inhale and project.
* I gargle with Listerine Original and drink loads of smoothies with pineapples because they are known to have antiseptic qualities (and taste brilliant).
* Singing is helpful. Once you get over the embarrassment, it's great to sing while you're cooking or driving to work. Singing strengthens the voice, exercising a vocal range you wouldn't use in conversation.