There is a headteacher who leaves his school at midday every Wednesday. "That's me away," he says cheerily to his depute, "and that's you in charge for the rest of the day."
As well as taking calls, dealing with disciplinary incidents and walking round the school to see what is happening, the depute also has some of the head's paperwork to attend to.
This particular head isn't lazy, as the heavy bundle of papers in his homeward-bound briefcase testifies. The purpose of his disappearance is to provide the depute with a full experience of managing a school.
On Thursday morning the head and depute discuss issues or incidents that arose during the head's absence. As well as useful insights and advice flowing from head to depute, new ideas and suggestions may also flow from the depute to the head. The learning is a two-way process.
The chance to be in charge of the school is also about job enrichment. A depute post can be frustrating and filling the head's "hot seat", even for half a day, can make the post that bit more interesting and fulfilling.
Preparing staff for future leadership roles should be a key part of every head's remit. I state "should", because in too many schools the head doesn't do much to prepare deputes for management roles.
As well as giving over the management of the school for a half-day, there are many other ways in which heads can prepare deputes, and others, for future leadership roles. One strategy is to send deputes to shadow effective headteachers in other schools for an afternoon or two.
A very experienced, capable and popular head retired recently and I asked him how many deputes, outwith his own school, he had helped to coach and mentor. He couldn't think of any. The local authority that employed him was guilty of failing to exploit fully one of its finest resources.
Coaching and mentoring are not just about learning from best practice. There is also much to be learnt from people's mistakes. At one useful management seminar, a jovial head talked through all the major mistakes he had made and what he had learnt from them. He joked that he had made so many mistakes that he was unsure whether he was put forward as a good example or a horrible warning.
But in one respect he certainly excelled: passing on his learning experiences to others. Because the final test of any leader is that he or she leaves behind other people properly prepared to take up the crucial role of leading a school.
Indeed, I remember one head going even further and stating, in his retirement speech, that his proudest achievement was being able to help develop members of his staff to surpass him.
John Greenlees teaches geography.