If you are a busy headteacher, you will know that at this time of year you suffer the tiresome inconvenience of staff begging for a day’s leave of absence next January to visit The British Educational and Training Technology Show (BETT) at London’s Olympia .

Of course, your answer will be “No,” but it is a sad fact of life that some teachers - especially those who are not on temporary contracts - have an unfortunate propensity to argue the toss. This will inevitably lead to “dialogue” - as blazing rows are now called. To prepare yourself for this confrontation, read on.

You say: “I know computers are your particular passion, but I can’t give days off to all the teachers who want to pursue their particular passions - I’d have requests for the Motor Show, The Boat Show, The Antiques Road Show - and, in certain cases, shows of a singularly unsavoury nature.”

Be on your guard. The barrack-room lawyers on your staff will claim that they are not interested in computers per se, but in the educational opportunities they afford. They will explain that there are numerous shows throughout the year devoted to various aspects of new technology, but BETT is unique in that all of its 400 to 500 exhibitors concentrate solely on how information technology can help schools to function more effectively.

You must quickly interrupt at this point. Try a curt reminder that such lofty matters are best left to advisers, educational researchers, directors of education and other movers and shakers for whom BETT is obviously intended. Teachers - generally a self-effacing bunch - are unlikely to argue with this.

Unless, that is, they know something about the 15,000 or so visitors who attended last year’s show. It’s true that 15 per cent were IT co-ordinators, 25 per cent were heads and deputies, but a surprising 31 per cent were ordinary classroom teachers.

Tut, tut vehemently at such statistics. Say how irresponsible it is for schools to allow that number of teachers to play truant and thus deprive their pupils of a day’s teaching.

Unfortunately, this line of attack isn’t quite as convincing as it might at first seem. An increasing number of schools arrange that at least one of their statutory in-service days coincides with BETT. So a few teachers - and, in some cases, the entire school staff - can visit the show without causing any disruption to the timetable. If you are told this, sigh volubly and explain, in as patronising a tone as you can muster, that visiting a trade show, however prestigious, does not constitute in-service training in your opinion.

Do not be surprised if you are treated to an equally patronising response. BETT, you will be told, offers the perfect opportunity to test-drive equipment and to subject manufacturers to the third degree. It also provides an unrivalled programme of seminars and lectures, covering everything from the nitty gritty of using computers in the classroom to heady speculation on the future role of IT in education.

Now play your trump card. Shake your head regretfully and say: “I see where you are coming from, but must be aware that the school simply can’t afford to send a member of staff to BETT.”

Beware. There are some teachers who might reply by shaking their heads and saying, “I’m sorry but the school simply can’t afford not to send someone there.”

You will be told that, whether it’s choosing equipment or planning for the future, BETT enables teachers to arrive at informed decisions. For that reason alone, it can save a school a small fortune - well worth the cost of a supply teacher and a cheap day-return to London.

Of course, you should not allow yourself to be swayed by any of these arguments. As you usher the teacher to the door, be avuncular. Explain that you enjoyed interfacing and valued his or her input (computer folk respond to this sort of language).

Ask for the request to be put in writing, and, when it arrives, file it in the rubbish bin. But not before you’ve made a note of the dates: January 14 - 17. You never know, you may feel that you ought to go there yourself.

* The TES speaker at BETT 98 will be Dr Linda Roberts, director of educational technology in the US Department of Education. Her talk is entitled: Preparing America’s students for the 21st century: the Clinton administration’s technology initiative.