Most of the time we understand this necessity in purely physical terms - a chance to recharge our batteries. Many teachers I know are packed and gone by the first Saturday of the holidays, fleeing the scene of stress and exhaustion and taking at least a week, if not more, to wind down after the busy turmoil of the year. Our bodies need the rest. But, perhaps more importantly, our minds need a break too.
I am no great fan of Samuel Johnson. His politics were conservative, his attitude towards women highly dubious. Yet he wrote eloquently on the virtues of "idling". This was much more than a call to mere laziness, which the word now implies. In essence, idling entailed being freed from the constraining timetables of everyday cares in order to liberate the mind.
Unfettered by the clutter of the mundane, Johnson argued, we are released into a place where we can think and roam intellectually.
For Johnson, of course, this was an activity to be enjoyed by gentlemen of a certain class and intellectual disposition. His own ability to idle successfully was supported by two infinitely forbearing women (who were convinced he was a genius), a number of wealthy patrons and a household full of servants. Such options are not open to many of us - any more than such overweening self-absorption is attractive.
Yet the principle remains a good one. For the opposite of idleness is not industry but a kind of vacuous business that fills the day with too little thought for the worth of any given activity. Though it gives the appearance of indolence, idleness can be hard work. It's as if the mind needs displacement activities to function creatively.
All of us recognise the desire to switch off when faced with a peculiarly pressing task. Whether it be clubbing, jogging, snoozing or watching television or, in the very idiosyncratic manner of a friend of mine, cleaning the oven, there are times when we need to do nothing in particular in order to complete a task.
But the difficulty with such activities is that they engender guilt and a degree of panic. They are not attending to the matter in hand - the writing of the paper, the completion of marking or the finishing of a report - and deadlines loom ever nearer. We are always racing against time, crushing too much into the available space.
If, like Johnson, we saw idling as part of the process, we would be released from some of that anxiety. We would feel confident that quality only comes from those who have had the time to contemplate.
But all this sits ill with the current philosophy of pace. For it is not only teachers who feel the relentless treadmill of forced business. I often feel exhausted at the end of a lesson observation by the remorseless rapid-fire questioning and sheer volume of stuff that pupils are required to complete. True, the room for disruptive behaviour is diminished - but so is the space to think. Children are bombarded with information and speed of calculation is held at a premium. Off-task behaviour is frowned upon, day-dreaming banned. Measurable output is all.
Yet which of us, on a training course, does not chat with a neighbour or let the mind wander? We need the mental break for the ideas to settle and to work out what we think of them. We learn as much, if not more, when we let our thoughts meander - in the bath or the shower, perhaps - and reflect on the day, as we do when we are taking notes. Extended periods of time with little to do can be even more productive.
So let us celebrate those legitimised moments of idleness in the summer holidays. Let us bask in the heat or relax in the rain. Let us mooch, pootle or party to our hearts' content and enjoy the seductive ease of the six-week break.
But above all let us use the mental space to contemplate ways of democratising the necessary luxury of idleness, and create a means of extending it into the busy grind of the school year.