Teachers don't have to endure Eliza's elocution nightmares, but speaking clearly can help you do your job better.
Barbara's car is a Jaguar, and Barbara drives rather fast.
Said aloud, this sentence will distinguish those who have mastered received pronunciation from the glottal stoppers, the upwardly mobile from those whose accents condemn them to the bottom of the linguistic heap.
And it will help teachers to be taken seriously by their pupils.
Olga Smith, one of the authors of Get Rid of Your Accent, a new speech-training manual, claims that teachers have much to gain from ironing out their glottal stops and estuary vowels.
"Accent and vocabulary can stamp a person's identity like a brand," she said. "If a person with a Cockney accent and a person with a public school accent apply for the same job, the public school person will be preferable."
And she believes pupils are more likely to respect teachers whose classroom instructions are not a swamp of glutinous vowels.
"Teachers who have graduated with PhDs have been mocked by pupils for their accents," she said. "If a teacher has a strong accent, their credibility will not be good. And if their speech is unintelligible, what can pupils learn?"
The book, which comes with two CDs, does not attempt to convert all readers to the Queen's English. Instead, it emphasises clarity and ease of communication. The aim is for users to acquire what Ms Smith refers to as a "neutral" or "standard RP" accent.
Anna Tunc is among those who suffered for her non-standard accent. For six years, the Polish emigre taught swimming to pupils in south London. But parents at one of the private schools at which she taught complained about her foreign accent.
"I felt I wasn't good enough," Ms Tunc said. "I lost confidence. But a teacher without an accent is always better assessed by parents. Some don't even want native speakers from Scotland or Australia."
But Gillian Brinded, head of Abacus primary in linguistically derided Essex, insisted accent was irrelevant.
"There's nothing wrong with having an accent," she said.
"I don't make mental notes about the way job applicants speak. I wait until I see them in the classroom. It's about using diction and grammar properly when you speak to children."