Modern life sometimes seems to consist largely of getting through barriers - “access control” is what this is called in the trade. Where the decisions as to who gets in are entirely subjective, there is no substitute for human judgment.

In other cases, however, automation, usually in the form of swipe cards or numbered keypads, is taking over. A step beyond, it seems, lies the world of “biometrics”. This is where a device homes in on the bits of you that are, within huge statistical limits, different from the same bits on any other person. There are many such body parts but biometrics concentrates on just one or two - the retina of the eye for example, your DNA pattern, or your fingerprint.

The machine takes a look, compares what it sees with what has been previously loaded into its memory, and decides whether there is a match. What happens then decides on the application: it can let you through a barrier, allow you to use a photocopier, or simply record the fact that you have turned up to be counted.

The advantage, obviously, is that while you might forget your swipe card, or have it stolen, or deliberately give it to someone else, you can do none of these things with your body parts.

Early biometric devices were big and expensive. Now, though, they are at the point where schools are starting to use them. Fujitsu’s Fingerscan, for example, is already used in a handful of schools. Kirkham Carr Hill High in Lancashire, for instance, uses it for registering the attendance of sixth-formers.

Margaret Wilde, the school’s deputy head, explains: “We wanted a system that would remove the need for a whole group of sixth-formers to turn up in a room for 10 minutes to be registered and then go away.” The time that is saved can be used for individual talks with students.

Highgate School in north London also uses Fingerscan, though in this case not for registration but to monitor attendance in the school canteen. Says deputy head Mike Buchanan: “The dining hall is a 10-minute walk, so we use the system to make sure the boys attend lunch.”

There have been relatively few problems. At Highgate, the sheer weight of numbers - 600 pupils queuing at lunch to be “scanned” - caused some difficulty at first, but things have improved as everyone has grown more used to the system. At Kirkham Carr Hill, Margaret Wilde finds that the way the system puts out its results “is not as statistically convenient as SIMS, which we use in the rest of the school”.

The business end of Fingerscan is a terminal with a place to put your finger. The machine “reads” your finger and compares what it sees with an internal database of, as it were, “pre-recorded” fingers. It notes the time of scanning, and the information is downloaded by cable to a PC. From there it is possible to see who “scanned”, and when.

It is extremely foolproof. Only occasionally may it fail to recognise a finger first time - perhaps because the person has arrived with very cold hands. This is because the system does not, as you might expect, simply read fingerprints, but recognises a three-dimensional image of the finger that includes colour and blood flow. Thriller writers, therefore, can forget the idea of cutting off somebody’s finger and using it to enter a high security building. For the same reason, people worried about civil liberties are assured that you cannot make the system produce a record of the fingerprints of the people who use it.

Undoubtedly more and more schools will become interested in this sort of technology - it has the advantages of a swipe card system without the associated security problems. If, and when, Fingerscan, or any other biometric system, not only comes down further in cost (so that there can be a number of terminals for registration) but is fully linked up to an existing computerised school registration package such as SIMS Attendance, then it will start to be a viable option.

A single Fingerscan unit, with storage for up to 350 users, starts at Pounds 3,000 plus VAT. Details from Global Security UK Ltd, Grove Court, Hatfield Road, Slough SL1 1QU, tel: 01753 554022