Good morning, animals. Siddown! It’s autumn. Season of mists. Exams just around the corner. You will turn over a new leaf! What will you do? Knuckle down! Understood? Good. Right. Eyes on the board, cretins! Do I have to spell it out, lad?”

This - or something like it - was how a science teacher introduced himself to a class of 14-year-old boys at a state secondary school in south London some 35 years ago.

No teacher would speak like that now, would they? The mixture of insult and cliche would not impress inspectors. Our teacher - sorry, master - got away with it because he used the idiom of his day, and of his profession. Such “masters” routinely resorted to this style of invective. He could safely assume his class got his drift.

“Idiom”, says my dictionary, is “the language peculiar to a people or district, community or class”. An idiom is an expression whose meaning “cannot be derived from the meaning of its individual elements”. I’d go further. Idiom is the live language, with all its faults, ugliness, difficulty and beauty. As opposed to the pure, dead language of grammarians.

As would-be teachers, should you be trying to reduce your use of idiom? Is there an equivalent, acceptable teachers’ idiom in 2003? The questions arise partly because we live in a more fragmented society, and partly because many more pupils do not have English as their first language. You obviously have to make yourself understood to all your pupils as far as possible.

Your English learners should be receiving extra language support from qualified teachers of English as an Additional Language (EAL), and in some cases, bilingual assistants. They can help you, as well as the pupils, overcome specific language problems. While you’re worrying about EAL pupils, you might also ask: how much sense am I making to the mildly aphasic girl in the corner, the boy who may be slightly autistic, the child whose Jehovah’s Witness parents have never allowed her to watch television? They all speak English and only English, but whose English?

Trying to strip your speech of all idiom, of anything whose meaning is not deducible from a dictionary definition of each word - is not recommended by any of the EAL teachers I consulted via the NGFL’s EAL-bilingual mailing list.

This approach is rejected outright by multicultural education expert Robin Richardson, director of the Insted consultancy. “Metaphors are the lifeblood of language and it is neither possible nor desirable to protect kids from them,” he says.

“Rather, teachers should monitor their own language so that they don’t make unwarranted assumptions about children’s linguistic experience and don’t cause avoidable misunderstandings.”

Richardson also makes the point that every teacher should be thinking about the language they use. Whether or not you have EAL pupils is “basically irrelevant”, he says.

Catharine Driver, head of Ethnic Minority Achievement amp; EAL at South Camden community school, London, agrees that attempting to simplify your language can backfire: “Simpler English can actually be harder to understand. I’d say clarify rather than simplify.”

She works with secondary teachers, mainly science and maths specialists, and advises them to use accurate technical words to explain concepts rather than attempting to paraphrase. “One word is better than 10.”

Elspeth Stewart, a peripatetic EAL teacher in Moray, Scotland, says she’ll “spend a bit of time teaching lists of idioms, and go through the meanings”. Sometimes her pupils will come up with parallel phrases from their own languages, which include Arabic, Cantonese, Estonian and Punjabi.

Both she and Catharine Driver find that most confusion is caused by another form of idiom, the dreaded phrasal verb. The deceptively simple-looking conjunctions of short verbs plus prepositions often carry a meaning which bears little or no relation to the literal meaning of each of the component words. Think, for example, of the many phrases starting with “get”. “Get over it” meaning “recover”; “get on with it”; “get on with” a person. And then, “don’t let him get away with it”.

Almost as much confusion is available from phrasal verbs based on “put” or “take” or “stop” or “see”. “I ended up going back to an old grammar book to look them up,” says Catharine Driver. “There are just so many in everyday use.”

In her opinion: “It’s often easier for a pupil to understand one long word rather than three short ones. Perhaps the easiest way of dealing with idiom is to make it a teaching point.”

Which leads us back to Robin Richardson’s ideal - that teachers “should encourage kids to take a lively interest in metaphor and idiom, and in the proverbs, stories and situations from which idioms and metaphors are derived”.

There are many ways of celebrating idiom across languages and cultures.

Pupils can be asked to collect, compare and illustrate idioms - or even make poems out of them, as teacher Pie Corbett does in An Odd Kettle of Fish.

‘What’s In a Word’, by Norah McWilliam (Trentham Books pound;14.99)‘Oxford Dictionary of English Idioms’, by Cowie Mackin and McCaig (Oxford University Press pound;20.50)‘Equality Stories’ and ‘In Praise of Teachers’, by Robin Richardson (Trentham Books, pound;13.99 and pound;12.99)