That is one reason why the terrible violation at Dunblane primary is so painful. It is a challenge to beliefs that underlie modern education. It is an invitation to turn our backs on openness and to shut children and their teachers away from the community to which they belong. Parents are repeatedly told that they are welcome in school, but must they now penetrate a security cordon to meet teachers and share in their children's education?
Rationally, we know that another attack like that by Thomas Hamilton is so unlikely that it cannot dictate the future. But emotionally we are less sure. After all, before last Wednesday no one would have said that in this country such an act was possible. Little wonder parents have hugged their children so tightly before seeing them off to school. Emotion and reason give different messages.
And so, as after the Jamie Bulger murder, there is a nagging worry that perhaps things have changed, that society has to accept, or at least gird itself against meaningless violence. And what if we come to countenance a level of wickedness, while still fighting it? In many American cities random murder is part of daily life and becomes unremarkable. To admit the probability of evil acts is only one step from seeing them as a norm: the trap into which the Third Reich lured so many Germans.
Again, is that too pessimistic, like some of the breast-beating in the Jamie Bulger case? Reason hopes it can say yes. But nevertheless there is comfort in evidence of normal decencies. Two days after the massacre, a bundle of school inspection reports arrived at our offices. It was reassuring to read the repetitive phrases which I and other commentators have on occasion mocked as bland and trite. In every school - primary, secondary and special - there is evidence that pupils are happy and staff are dedicated.
At Tarland primary in Grampian "all parents felt that their children enjoyed school". Pupils of Castlehead High in Paisley "were very positive about the school". Harmeny, a school in Balerno for children with emotional and behavioural difficulties, "had a warm and welcoming ethos".
In other words these are schools with the characteristics of Dunblane primary and nearly 3,000 other schools in Scotland. Whatever new measures have to be applied to make schools more secure, there is nothing amiss with the way they go about their job. Neither Thomas Hamilton nor fear will destroy what is good.
Hamilton took cruel advantage of the openness of buildings. He also struck at another of the principles of education today. Schools, everyone agrees, should be a community resource. They should not lock their doors at 4pm and keep them shut throughout the holidays.
Across central Scotland Hamilton set up boys' clubs in schools. Most lasted only a short time before parents became suspicious and withdrew their children. But on the surface he appeared to be offering a voluntary service, and so was given the use of buildings. Community education would be the official umbrella term for what he was ostensibly advancing.
Only now is it clear that he was manipulative, perverted and increasingly twisted. His was a defilement of community involvement. The question for the future is how to ensure that school lets are strictly monitored. No one expects rigorous checks on an individual or organisation that seeks to hire a room once. But surely there has to be proof of good intent from those wanting to set up a regular base, especially if the aim is to attract the young.
Will smaller local authorities and devolved management make checks more problematic? If a register of undesirables is to be kept, probably yes. But if school boards decide who should hire rooms, local knowledge (and even the level of unsubstantiated suspicion which attached to Hamilton) may be an effective safeguard.
One cause for optimism is sure. Dunblane primary has shown it has the staff to make it again a happy place for children. In that sense it is no different from anywhere else in Scotland.