The human ear has evolved over millions of years into a wonderful instrument almost perfectly adapted to its purpose which, as any craftsman will demonstrate, is to hold a pencil. "That's the one thing we never have to teach the kids," says Len McDermid, of the Rude Mechanicals' Workshop, as he surveys the class while they saw their pieces of wood, their pencils perched precariously behind their ears.
But,of course, it is the adult ear that nature has designed, and the infant version is by no means as suitable for the job. So the first problem the youngsters at Fallin Primary near Stirling have to solve is getting their pencils to stay put. And of the various possibilities some- such as stabilising it with a piece of gum - are a lot better than others, like shoving it in your ear instead of behind it.
And although all this is somewhat peripheral to the main aim of the workshop, which is to learn how to make components and assemble them into a machine, it does illustrate what it is about kids that makes them so rewarding and challenging to teach: whilst trying to imitate adults they almost invariably add little twists of their own, whether just to be different, or because it looks like an improvement, or simply to give themselves and their pals a good laugh.
One of the advantages of workshops such as this is that vaiations, mistakes and creativity can be accommodated more readily than in a normal classroom setting where teachers are tied quite closely to the curriculum.
"It's a bit like a road that we take them on," says Dick Warren, "and we can linger at any of a number of interesting places along the way."
But in a one-hour session the presenters are rather more constrained than if they were spending, as these ones often do,a whole day or several days in school. And the only criticism that could possibly be made of this enchanting workshop is that it is not long enough.
Even so, a casual observer who dropped in at the beginning of the show and then again at the end would find it hard to believe that simple tools and materials such as saws and wood could, in such a short time, produce miniature working cranes - and smiling and delighted children. Unless there was some kind of magic at work.
And in a way there is the magic, sparked by creativity and good humour, which puts new skills in the hands and memories in the minds of a classful of children.
The Rude Mechanicals' workshop Up, Down, Turn Around can be adapted for children from Primary 1 to 7. The principals run science and technology workshops for primary teachers and pupils throughout the year; tel 01573 440537. EISF box office, tel 0131 555 6626.