Traditional security techniques have a fair track record. They attempt to minimise the risk of crime by increasing the likelihood of eventual capture. It is hoped that they will persuade potential attackers either to abandon their enterprise or find an easier target. This approach will be less successful when the attacker has no desire for loot and is unconcerned by the possibility of capture.

Security buys time through a balanced combination of detection systems and well chosen physical and psychological obstacles. The intention is to slow down an intruder’s progress and give the authorities time to respond. In the case of personal assault, the aim is to buy enough time to allow those under threat to flee to a place of safety or to implement arrangements to isolate, subdue and restrain an attacker so that there is no longer any threat to staff or pupils.

Mass flight is an unlikely scenario, nor should school staff attempt to restrain a violent attacker. This leaves only isolating an intruder while calling for expert assistance. Few have bothered to ask if the systems schools are installing to guard against personal attack will buy the time it will take for assistance to arrive and become effective. Possibly some have not even enquired how much time they need to buy.

It may take only seconds for a signal to flash from a personal attack alarm to a control room and then on to the police or guarding company, but several minutes will pass before assistance arrives at the school. Even if a school relies on its own security staff, there will still be a delay as they gallop to the scene.

Security does not come cheap. This is especially true of electronic systems. To cover a school completely with closed circuit TV cameras will be expensive and anything less is open to criticism. To be effective, the pictures must be watched in real time all the time the school is occupied. The cost of providing office space for this will be low compared with the cost of employing staff to watch the pictures.

In the world of electronics, obsolescence is life. This morning’s gleaming state-of-the-art equipment is this afternoon’s dusty museum piece whose effectiveness can only be maintained by replacement and renewal.

Access controls, whether passive ones using fences, active ones using smart cards or real-life guards, also suffer from the fact that school entrances and exits are an eternal weakness not just when pupils are coming and going but when visitors arrive, deliveries are made or contractors are working on site.

Enthusiasm is at its greatest immediately after an incident. This can obscure the unpalatable truth that all security is an encumbrance. It is tolerated when the need is obvious but, as weeks and months pass without incident, support diminishes to a point where perfectly good security measures are ignored or circumvented, often with the tacit approval of those in authority.

Schools must take adequate steps to protect children but, in dismissing a claim for damages against a school, Judge Zucker said last June that a balance must be struck between maintaining security and turning a school into a fortress. No school could prevent accidents; they could only take sensible and proper steps to safeguard their pupils. The challenge is in using foresight to identify those steps.

The pressures for action are great. There is the reassurance of being in step with the majority, protection against future criticism and the knowledge that the questions raised by governors, staff and parents are answered if not satisfied. Include manufacturers’ claims that they have the ideal solution and the urge is nearly irresistible.

It is a straightforward choice. Take the easy route of instant action. This is the M25 of decision-making and will give a feeling of having travelled hard and far. Or search less frequented byways for a sensible answer that meets the needs of the pupils.

Alastair Buchan is a former assistant director of education in Sunderland and a founder member of the North-East Risk Management Group