Spot the difference. Here are the first few words of a Year 11 English assignment that will get a borderline grade C at GCSE: “In the book, the writer says .”

Now here are the first words of one that is likely to gain a grade A: “In the novel, the author suggests .”

The difference, I contend, has little to do with intelligence; it’s about vocabulary. For too long we have let the main influence on a child’s vocabulary be the variables in their background, so that those who come to our classes knowing words like “suggest”, “assert” and “propose” will be the ones who get into the top sets and finally progress to the top universities.

Vocabulary, we now realise, matters a lot. In his book The Mating Game, Geoffrey Miller suggests we listen covertly to the lexical level of our prospective partners to see whether we are well matched. Size clearly matters. We do not want a partner with a vocabulary level significantly different from our own.

In schools, we know that students are judged by their ability to express ideas in appropriate ways. The one who uses “says” instead of “suggests” or “but” instead of “although” may seem to signal that they are less intelligent than their peer sitting next to them. In reality, they may just have a narrower vocabulary.

That is why a key element in any English classroom should be recognising the essential vocabulary our students need, from technical words like “rhythm”, “enjambment”, “prose” and “connective” to generic words like “imply”, “assert” and “propose”.

But this alone will not be enough. Great teachers use rich vocabulary, often picking words that are pitched beyond their students’ comprehension. But in their explanations and descriptions they artfully explain the terms they are using.

It is a technique that seems effortless in the presence of the best teachers. For the rest of us, we need to learn, practise and remorselessly repeat the approach throughout our lessons. Our students will then develop the vocabulary to move from learners to experts - irrespective of their background.

Geoff Barton is headteacher of King Edward VI School, Bury St Edmunds, where he teaches English

WHAT ELSE?

Try a vocabulary-building exercise from TES English to establish alternatives to “said”, “got”, “went”, “big” and more

For classroom displays try geminiwhizz’s alternative word squares

Make your pupils’ writing more imaginative with material shared by soxy14

In the forums

Teachers discuss their ideas on how to broaden vocabulary in school and at home

All resources and forum links at www.tes.co.ukresources009.