Fortunately there are few murdering Thomas Hamiltons. There are, however, those who have a grudge against schools, teachers, children, society or whatever. Consequently education authorities, school boards and headteachers must reassess the balance between accessibility and security. They must all ask themselves if they have taken every reasonable step to prevent another Dunblane.

It is doubtful whether any building can be totally safe. But we can take steps to limit the potential for such a tragedy. Recently I walked into a school, looked into several classrooms and finally found the person I was looking for. Nobody challenged me although I was, to all intents, a total stranger.

We are so trusting and yet the care of several hundred lives is an awesome responsibility. In many smaller schools there are possibly no full time administrative or janitorial staff in the school and the headteacher is probably class committed. All the staff assume that the stranger is an expected visitor and yet the Dunblane incident is not the only occasion in which a stranger has attacked children, in a school.

How can we limit the risks? There are several ways. First, we can limit access to particular parts of the building thus protecting teachers and pupils from the danger of a stranger entering the classroom. This can be done fairly cost effectively with smart cards controlling the access doors.

Second, we can provide teachers with an alarm system which would enable them to call for help. It may be that a teacher has been surprised in her classroom and wants to inform her colleagues without letting her assailant know. This can be done effectively with a transmitter-like key fob.

Third, especially in secondary schools, we need to have an accurate register at all times of where pupils are. Single-period truancy is a common feature in secondary schools. Pupils know which staff keep a record and which classes they can miss and not be missed. Again an efficient way of doing this is to use a smart card system for tracking pupils throughout the day.

The system which I have used is based on a network of card readers which send information to a central computer. Each student is given a card which contains unique information. The card is swiped through the card reader and the information is transmitted to the central computer. In this way, students are tracked throughout the day as they enter or leave classes.

The card readers can also be used to transmit messages or instructions to staff. The reader emits a “beep” to indicate that there is a message and this is repeated at regular intervals until cancelled. Equally, the reader can connect with a key fob-type transmitter to pass a message from a classroom that help is required. The cards can also be programmed to allow access to certain areas only. This might be particular classrooms or indeed any part of the school other than the reception area.

There are several systems on the market that will undertake some or all of those tasks. I have had some experience of an integrated system which will do all of those things and more. The system I used was the Sentinel System manufactured by Radun Controls. Such systems are not cheap but they do save teaching time and enhance accountability.

Ultimately our parents expect that their children will be in a safe environment when they attend our schools and for most of them for most of the time, this is true. But we would be naive if we thought there was only one Thomas Hamilton.

Alan Cameron is a former headteacher of Ellon Academy. A pamphlet on the Sentinel System is available by sending a stamped addressed envelope to Alan Cameron, 5 Fechil Brae, Ellon, Aberdeenshire AB41 8NS.