Their nightmare typically involves arriving at school and having difficulty finding their class. When they reach their pupils, they realise they are woefully unprepared.
"I had no register, no scheme of work or lesson plan, and just a vague idea that I should be teaching something about polygons," said one secondary teacher. "Oh - and no whiteboard markers. The kids were just starting to get frustrated and starting to misbehave when I woke up in a cold sweat."
Teachers on the TES online staffroom have been struck by the uncanny similarities between their nightmares.
"My most vivid one so far involved me taking over a GCSE class from my own A-level teacher - who taught me 22 years ago - and he hadn't marked the coursework properly," one said. "I don't even teach GCSE."
Ian Wallace, an Edinburgh-based dream analyst, said he had heard similar nightmares described by teacher clients.
"What's happening is classic performance anxiety," he said. "It means that they set themselves high standards, so in real life they usually do a good job."
Mr Wallace said teachers who dreamed they were teaching the wrong subject were often at a career crossroads and should be thinking about promotion.
He suggested teachers ward off anxiety dreams by "reflecting in their waking life on their accomplishments as a teacher".