There are several tools that are vital to any teaching job: a red pen, a whiteboard marker, a class register - and a stick of deodorant.
A survey of 2,000 teenagers, published this week, has revealed that 46 per cent of them think unpleasant body odour a trait common to teachers. This tops even such cardinal sins of the classroom as "perving" on students, having coffee breath, or telling bad jokes.
This attack on the personal hygiene of the profession forms part of a national teaching survey, conducted by teen magazine Bliss. Boys and girls, with an average age of 15, were questioned, with 80 per cent of respondents attending comprehensives. Science staff were labelled evil and boring by 20 per cent of teenagers.
But even malevolent science teachers fared well compared with their maths colleagues, who were labelled "most evil" by 25 per cent of pupils.
Helen Johnston, editor of Bliss, said: "Teenagers don't just blanket-hate teachers. When they are well taught, they find it fascinating. Though it still makes sense for teachers to put on deodorant in the morning and wash their hair."
Often, she added, an inability to relate to subject matter leads teenagers to characterise teachers as despotic villains.
"Maths is traditionally one of the hardest subjects to teach," she said.
"It's pretty dry. So maths teachers are on to a bit of a losing battle.
"Teachers need to make the subject relevant. They could dip into the world of fashion or sport, looking at Beckham's bank balance, Britney's clothes allowance, or the technology of texting." They might also benefit by following the example of PE teachers, who were voted the "most sexy" by 49 per cent of respondents.
"They're the fittest, and they show the most flesh," Ms Johnston said.
But Barbara Bull, of the Association of Maths Teachers, does not believe that lunch-time laps around the playground would help her members. "Maths teachers can be sexy as well," she said. "I've worked with some who are the sexiest teachers in their school. I don't think Bliss magazine is in a position to tell us how to teach."