One of my favourite education articles is by Peg Tye, in the Atlantic Magazine back in 2012. In The writing revolution she describes how learning in a Staten Island high school was transformed by a curriculum-wide commitment to teaching the skills of good writing, based on evidence that the students’ inability to translate thoughts into coherent prose was severely impeding their intellectual growth in many subjects.
Typically, students right up to 12th grade were capable only of writing short, disjointed paragraphs.
Good writers, contrastingly, could use coordinating conjunctions to link and expand on simple ideas, using words like "for", "but" and "yet" as tools to express more complex ideas.
Furthermore, the use of dependent clauses such as "although" and "despite" give the writer the means to qualify an idea.
To that end, teachers began to challenge students to begin sentences with "although", "unless" and "if". (Ironically, the current vogue for beginning sentences with an emphatic "so" appears not to satisfy this requirement.)
The emphasis on writing is given substantial support in a book by David Olson, published last month, The Mind on Paper. Olson, a cognitive developmental psychologist, asserts that literacy is not simply a tool for reasoning – it is the very medium through which intellectual development actually takes place.
Writing is a tool for thinking, to be sure, but it is more than just a resource; it actually creates the conditions for higher order thinking.
Olson argues that the ability to think abstractly, to think about thinking, does not come developmentally, but comes through literacy. Written prose is not just preserved talk; it is an intellectual activity in itself.
It is through reading and writing (and the reflection on language that these involve) that we have mastered the ability to link and qualify concepts, to apply the "rules" of logical argument, and to distinguish between claims, inferences, tautologies and allegations.
Prose form makes possible the use of subordinate clauses linked by "because", "even though", "previously".
All of this, he argues, would be impossible in purely oral societies, because it requires close scrutiny of the very structure of discourse, using understandings that only come through literacy. Critical thinking would simply not be possible without writing.
That’s not to say that non-literate or poorly-literate individuals are not intelligent or do not think. According to Olson, "ordinary" thinking involves using language to talk and think about the world and to justify our beliefs and actions by appeals to reasons.
But higher-order thinking entails scrutiny of the language used in that thinking, and is only really possible with literacy. Writing is instrumental to such thinking.
This gives support to teachers of all subjects who push students to develop their understanding through writing, because it doesn’t just allow them to express their more sophisticated thinking; it actually helps them to secure and develop that thinking.
This applies to encouraging students to extend or re-organise their sentences, but it also underlines the case for giving students as many opportunities as possible for extended prose – "write" across the curriculum.
Dr Kevin Stannard is the director of innovation and learning at the Girls' Day School Trust. He tweets as @KevinStannard1