Teachers should be given microphones and voice training to prevent incurring serious injury to their vocal chords, says a leading throat specialist.
Dr Julian McGlashan, a consultant specialising in ear and throat problems at Queens Medical Centre, Nottingham, is treating at least one teacher a week with damaged vocal chords.
"Teachers can put their voices under enormous pressure," he said. "By the time I see people the damage is often done."
Dr McGlashan has enlisted the Professional Association of Teachers, to warn others of the "largely preventable" dangers. The union is also calling for microphones in classrooms, voice training to become mandatory for trainees and available for existing teachers.
Five years ago primary teacher Ken Hasler woke up without a voice. He said:
"I thought it was a touch of laryingitis, that I'd give it a week and be back at school. After resting all summer, it went again on the first day of term."
After seeing several specialists - "one looked at my throat and laughed 'Oh, you've got vicars' and market-stallholders' disease" - Ken is "forcibly retired" and living on incapacity benefit.
He said: "My voice is so weak I can't even answer the phone. The hardest thing to bear are people who think I'm making it up."
David Brierley, PAT solicitor, has seen hundreds of careers ended through voice loss. "Teachers who report problems are often not taken seriously, being told to 'stop shouting' or that it's an 'occupational hazard'.
"Teachers have to maintain good order in the classroom, but many have to struggle to be heard in schools that are overcrowded, badly designed, poorly ventilated and noisy. Stress can also make it worse."
Mr Brierley said: " There is no mandatory requirement for teachers to receive voice training, but employers have a legal requirement to provide a safe working environment, yet few seem aware or are willing to do something about this."
Ken Hasler agrees: "Actors and singers have voice training and they don't use their voices nearly as much as teachers do, and they have the advantage of an audience who wants to listen to them."
PAT has a factsheet 'Voice Care for Teachers, (Pounds 1.20 incl. p+p for non-members) available from PAT, 2 St. James Court, Friar Gate, Derby, DE1 1BT. Tel: 01332 372337