You might conclude that this is absenteeism on an alarming scale. But you'd be wrong. On the contrary, the annual mass evacuation during the last week of term is devised to prevent the seasonal drop in attendance. Every year, Deans holds an "education for leisure" week - this is the school's 19th - to give 800 pupils simultaneously an opportunity to celebrate the end of the session. "It was generally recognised that the school tended to wind down; we felt the need to provide a highlight," says Jim Jamieson, the assistant head.
Mr Jamieson was in at the beginning. He explains that the scheme was introduced by a former head at Deans who brought the notion of a suspended timetable with him from England.
Following the head's departure, Mr Jamieson took on the task of leisure week co-ordinator, a job he continued for eight years. "Planning started before Christmas, when we negotiated what was possible in terms of cost and manpower. "
The starting point is tutor-group discussion about possible activities; at the same time, a questionnaire is circulated round staff. Pupils' interests tend to dovetail with what teachers are willing to volunteer. Some demonstrate great ingenuity: "A PE teacher once organised 'Kidnapped revisited', a hill-walk following Alan Breck's trek across the heather." Golf (Jamieson's personal favourite) has been standard for 12 years and incorporates the school championship, played on various West Lothian courses.
Arrangements demand the forethought of a master tactician - nowadays, the job is overseen by a committee of four teachers. Transport is essential: "We book up all the local authority minibuses early in the year, usually ten for each day plus four 50-seater coaches," says Jamieson.
Between December and Easter, activities are drawn up in lists with "option boxes". Three choices per pupil allows for flexibility. This year, pupils have selected from, among other offerings, a dolphin safari on the Cromarty Firth, a trip to York, mountain-biking in the forests around Peebles, aromatherapy, "walking for softies" (with barbecues) and a photography work-shop.
One of the most popular of 30 options is the "TV spectacular", a chance to film various other activities on location, conduct interviews and then screen the finished film on the last day of term. Sometimes a new experience can have far-reaching consequences. Mr Jamieson once instructed a sailing course. "Two of my sailors are now captaining their own chartered yachts and taking millionaires around the Mediterranean," he says.
He admits he would be spinning a yarn if he claimed leisure week drew 100 per cent attendance. But he firmly believes it provides a high note on which to end the year. The staff don't regard the venture as wholly recreational either: team-building is a valuable outcome. Most significantly, the assistant head says, "It's the one time teachers come in for some genuine appreciation. Parents come in specially to thank us, as do participating adult students. Even pupils who were dragging their feet seem pleased."