While a mature H.Dip.Ed. student, a guest lecturer who was himself mature and who clearly knew his trade, gave us an example of how he went about the teaching of English: 'I hold up a piece of chalk to them,' he said, 'and say, "write me an essay about that."

He meant that mere recitation of learned facts served little purpose here, that the imagination and fantasy would have to be given free reign: what is chalk in the first place? Where might you see it in its natural state? Would Einstein have preferred a flip-chart, if such had been to hand in his day?

While myself guest lecturing in a National School, I brought along the grandchildren's playroom easel – it served much better to animate the tale of Giotto drawing the perfect circle; it also delivered graphic illustration in less time than felt-tipped pens (instant gratification, retained attention) and was more effective in adding colour, supplying, in effect, a speeded-up animation of the drawing process.

Yes, silicosis must be taken into account, but I would take the risk every time when it is only an occasional presentation and where the chalk medium suits the message.

Patrick Hennessy's 'Two Nuns walking on a Beach' (1948) with its clever contrast of the black-and-white figures dwarfed below the immensity of the Seven Sisters chalk cliffs near Dover conveys better than any photo the grandeur and natural majesty of the scene (the geology teacher may note for the pupils that the nuns are standing on what is known as a wave-cut platform).

The squeak as chalk meets slate will raise a howl, but with a little calm good-humour on the part of the teacher that won't disrupt proceedings unduly.