Panic buttons are set to be installed in Birmingham schools so teachers can call for back-up when confronted by violent pupils.
The move comes in the wake of growing concern over the safety of teaching staff in classrooms.
Earlier this week a 16-year-old pupil was jailed for the brutal rape of a 28-year-old teacher in London.
Figures from the Department for Education and Skills reveal 9,880 pupils were excluded from British schools last year, half of them for aggressive behaviour.
The figure for Birmingham was 273 pupils.
Three schools in the city have now expressed interest in installing panic alarms in classrooms.
They are being pioneered by a company that has introduced a similar system to GP surgeries to alert help when staff members are being attacked by patients.
Essex-based telecoms firm NEG is targeting Birmingham in the wake of recent evidence showing expulsions from city schools have increased by 50 per cent in the last two years.
Richard Chapman, chief executive officer of NEG, said: "Sadly, violence, truancy and anti-social behaviour appears to be on the increase in schools - and Birmingham is not alone in this."
Ill-discipline has been cited as one of the chief causes for teachers leaving the profession.
The Government has responded by pledging a zerotolerance approach to bad behaviour. It is pouring £220 million a year through the Excellence in Cities initiative and Behaviour Improvement Programme into tackling the problem.
But Mr Chapman said: "Ruth Kelly is urging a zerotolerance approach to this sort of behaviour, but that doesn't actually offer staff any form of defence against violence." NEG refused to name the three schools that have made inquiries about installing the alarm system.
But the firm believes it is likely to become as common a feature in schools as in GP surgeries where some 500 have been installed so far.
Figures from the DfES show nearly 1,000 pupils were expelled from schools across the West Midlands last year.
Birmingham had the highest number of pupils expelled from primary school nationally, with 47 permanent exclusions.
Education chiefs in Birmingham said measures to safeguard teachers were up to individual schools.
Headteachers yesterday demanded a tougher stance on unruly pupils and urged Ministers to give schools more power to exclude them.
The National Association of Head Teachers said bullying and racial or sexual harassment must be treated as " serious offences" and all violence regarded as "intolerable".
Panic alarm buttons would most likely be fitted under the teacher's desk. They could be linked to an alarm either in the school corridor or reception area to alert managers when a member of staff is in difficulty.