Teachers at a Caerphilly high school say disruptive pupils leave them fearing for their safety and others'.
24 teachers at Lewis School Pengam say they won’t teach the pupils concerned unless action is taken to control their behaviour. They have successfully balloted to refuse to teach the children until adequate action is taken.
The teachers’ union the NASUWT said the disruption had become a matter of health and safety.
NASUWT local organiser Chris Beggs said: “Members feel it is unsafe dealing with these pupils..."
“Low level disruption is one thing but when you have a group of pupils who regularly disrupt and are causing disruption to others you have to say that enough is enough and you are responsible for all pupils.
“The school will know who those pupils are and it’s a matter for the school to take the next steps.”
A spokesperson from school and Caerphilly Council said: “We are fully engaged with the union and the teaching staff at Lewis School Pengam to ensure that any concerns raised are addressed.
"All schools face challenges with pupil behaviour at times, but it is important to stress that there are appropriate procedures and support mechanism in place to manage these situations.
"Lewis School Pengam has an excellent track record of attainment and of managing pupil behaviour appropriately, so we are confident that we can bring this matter to an amicable resolution in the interests of all concerned.”
NASUWT's national official for Wales, Neil Butler, added: "If we feel health and safety is under threat by teaching a child or children we give the school the opportunity to deal with that situation to make sure our members are safe.
“We gave the names of the pupils to the school and asked them to sort it out. Talks are continuing.”
The dispute is one of a number the NASUWT is currently engaged with employers around Wales.