"Another Dunblane" is inevitable unless schools improve their security, it was claimed at the annual Scottish conference of the NASUWT union in Cumbernauld.
Union member and health and safety trainer John Henvey said the tendency for schools to have two or three entrances made them easy to get into.
Delegates supported his motion stating that "school security had been allowed to lapse in recent years and that another violent tragedy could easily occur".
He was backed by Joe Foy, a colleague in the union's South Lanarkshire branch, who said that "we know there is going to be another Dublane", in reference to the events of March 13, 1996, when Thomas Hamilton killed 16 pupils and a teacher in Dunblane Primary, before committing suicide.
Debate around the motion also focused on violent pupils who get moved from school to school.
"We should refuse to allow these pupils into classrooms," Mr Henvey said. "We also have the right to work and live in a safe environment - health and safety in schools should not be compromised."
The union will call on the Scottish Government to make entry secure at all Scottish schools.
Mr Henvey, a retired teacher, raised his concerns after visiting 40 schools in places as far apart as Brechin and Lockerbie.
- Members agreed that the chartered teacher programme had "become a barrier to teachers obtaining a higher salary", because of the costs and time required.
"The fees must be abolished, the workload must be reduced, and the scheme must be open to everyone," said Victor Topping, national executive member.
Mr Topping also questioned whether the scheme, by recognising the good practice of a select few teachers, implied that other teachers were not good at their job.
- There are mounting concerns about the "demanding schedule" for implementing A Curriculum for Excellence.
The union wants to arrange a meeting with the Convention of Scottish Local Authorities and the Association of Directors of Education in Scotland "as a matter of urgency".
Their aim is to ascertain how the new curriculum can be implemented within existing contractual arrangements, without adding to teachers' workload.
- "Someone is going to get killed" unless drastic action is taken against pupils carrying knives, or any implement that could be classed as a weapon.
That was the claim from treasurer Roy Robertson, whose call for permanent exclusion of pupils carrying any such implements was backed by his union colleagues.
- The "heinous practice" of allowing teachers to teach subjects in which they have no qualification must be stopped, the union believes. It will take up the issue with the General Teaching Council for Scotland.
- The union is to investigate the possibility of action being taken against the hosts of controversial website ratemy teachers.com and similar web-sites, where it can be shown that they are failing to act on teachers' requests for removal of material.
EARLY INTERVENTION CAN REDUCE STREET VIOLENCE
Failure to intervene in troubled babies' lives can have drastic social and financial effects when children grow older.
Developmental psychologist Suzanne Zeedyk told the NASUWT's annual Scottish conference that pre-emptive measures were the best way of tackling children's bad behaviour.
Dr Zeedyk, a developmental psychologist at Dundee University, explained that babies intuitively knew to respond to events around them: she showed a video clip of a father sticking his tongue out at a baby born only 10 minutes previously - to which the baby stuck its own tongue out.
So a baby not surrounded with such stimuli, perhaps because its mother is depressed or because its heroin-addicted parents lead a chaotic lifestyle, is deprived of an environment that is crucial to its early development.
Studies have shown that the brains of babies in such surroundings do not grow like those of other children, and the lack of routine and stimuli means they react to the world differently.
"When people are what we might see as misbehaving, it's not just because they want to misbehave - it's very often because that's how their brain is making sense of the world around them," Dr Zeedyk said.
She believes the "key to reducing violence on the streets is early intervention". It is possible to make a difference when children are older, but "it's harder, more expensive, and less likely to be successful".
Dr Zeedyk acknowledged that any attempt to introduce early intervention on a significant scale could be badly hindered by the difficulty of getting different sectors to work together, and by governments' unwillingness to look beyond the next few years of their term in power: "There are huge problems in the way we fund our systems."
She stressed, however, that there were good examples of early intervention in Scotland and the rest of the UK. These included Parents Altogether Learning Support - a Dundee-based parenting programme, better known as PALS - and work by the Scottish Violence Reduction Unit.
Dr Zeedyk also pointed to missdorothy.com, a scheme rolled out to every school in London which helps children to manage risk.