ON THE monitor the red line suddenly leaps skyward.
Is the photocopier broken again? Is it Ryan Smith's mum asking for an interview? Or is it just the Year 12 class from hell?
Guinea pig teachers agreed to have their heart rates and blood pressure measured during a normal working day. Watching the screen from a caravan in the playground, psychologists charted how staff reacted to the stresses and routines of the job.
Teachers' TV is making a documentary called How Stressed Is Your School?, but it has already been dubbed "Badger Watch with Teachers". A film crew has beenfollowing eight volunteers around Kings Langley school in Hertfordshire for five days.
The staff were trussed up in blood pressure cuffs, pedometers and high-tech "stress vests" to measure heart and respiration rates and body temperature.
The psychologists from Queen's university, Belfast, watched their subjects'
every move. Mouth swabs were extracted regularly to test for cortisol, the "fight or flight" stress hormone. Then staff were interviewed about their day. Any stressful moments were matched with the physiological data.
All staff were asked to fill in a stress questionnaire. DNA samples were taken for research into the link between stress and genes. The results proved fascinating and occasionally startling.
Two members of staff were identified as "incredibly exhausted" by the questionnaire alone.
Nadia Wager, an occupational psychologist, identified the main stress points that sent blood pressure spiralling and heart rates racing: photocopier breakdowns and dealing with parents. Disciplining pupils was also guaranteed to send readings off the graph.
"The measurements were more likely to go up when they are hiding their emotions," she said. "If there's a discrepancy between displayed and felt emotion, that leads to high blood pressure."
All the staff started the day with very high levels of cortisol, in anticipation of the day ahead.
Chris Peirce, an assistant headteacher at King's Langley, proved interesting: his blood pressure actually dropped while teaching. He said:
"It is the most relaxing part of the job for me as there is no phone, email or outside pressure. It is just me and a class of kids and I feel in control."
Emily Creed, 24, a music teacher, said her low blood pressure shot up when her head of department came into the room. Paperwork for her was the most stressful aspect of the job, as well as fitting in after-school meetings and other events.
Helen Goodchild, who deals with more difficult pupils, said: "After seeing the results, I was surprised by how much things were affecting me.
Sometimes I didn't even realise I was so stressed. Luckily though, they said I was quite good at letting go of it when the problem had passed."
The school caretaker was also involved. His pedometer readings showed he clocked up an average of seven miles a day.
Gary Lewis, the headteacher, said the school had launched several simple initiatives to reduce staff stress. He said: "I invite the staff for regular sessions of wine and nibbles on Friday nights so they can talk about their issues.
"We have also taken on a tea lady in the staff room so tired teachers don't have to wait so long for their hot drinks at break." Mr Lewis, who described himself as a "coper", said it was hard to say which members of staff had the most stressful job.
But Mr Peirce begged to differ. "It's the head," he said.
The experiment will be shown over five episodes on Teachers' TV next week.
"We wanted to look at the school forensically, from a scientific point of view, using cutting edge physiological tests," said Robin Kent, the series producer. "It was interesting to see how people teaching could appear fantastically calm while their heart rate showed the opposite."
But staff can comfort themselves that they do not have the most stressful occupation.
Giannicola Loriga, product manager at Smartex, a textile company pioneering the "stress vests", said: "We've tried the vests out on firemen doing their job, and their readings were higher."
Teachers took around 600,000 days off last year because of stress, anxiety and depression, a survey of local authorities has found. Around 150 teachers were absent for the entire year because of stress-related illness and around 500 others left the profession while on extended sick leave.
How Stressed Is Your School' will be broadcast on Teachers' TV from Monday to Friday, February 19 to 23 at 9pm.
What the stress vest revealed
The top five triggers of stress in the school day as measured by psychologists from Queen's university, Belfast working at King's Langley school, Hertfordshire
1. Problems with the photocopier.
2. Confrontations with parents, either face-to-face or on the phone.
3. Dealing with difficult pupils.
4. Keeping up with paperwork, emails and phonecalls
5. Having lessons observed