A small percentage of secondary heads are refusing to exclude persistently disruptive pupils who are causing "fear and alarm" across the school community, the Scottish Secondary Teachers' Association has claimed.
Although its general secretary, Ann Ballinger, welcomes recent Government statistics that showed an 11 per cent fall in exclusions to 26,844 instances in the past academic year, she called for more widespread use of alternative methods of support for "troubled young people".
"Restorative justice, staged intervention and the use of organisations such as Skillforce have produced gratifying results in a number of establishments, enabling young people to learn appropriately and teachers to work in a calm and supportive environment," she said.
Ms Ballinger accused some headteachers of practising a "you shall not exclude" commandment and, in so doing, putting at risk the education of the well-behaved majority of pupils.
Ken Cunningham, general secretary of School Leaders Scotland, said: "I don't know of any heads who don't share all staff's concerns for ensuring good behaviour in schools."
But his members did what they could with the resources available to them. The process of exclusion and placing pupils in other institutions could be complex and expensive, he added.
Education Secretary Michael Russell said: "I accept that some schools don't want to exclude young people because they don't think it's good for them. But I think they all know that sometimes, very occasionally, that has to happen. I have no evidence that in circumstances where it has to happen, it doesn't happen."