One thing seems certain: Just giving out more writing assignments won't do the trick.
What are we to make of the seemingly miraculous success of New Dorp, the high school that is the subject of Peg Tyre's recent Atlantic story? The history of education is littered with flavor-of-the-month interventions, many of which began at a model school, but that, once implemented elsewhere, flopped. Dejected educators then begin scouting for the next "big thing."
In this instance, a heavy emphasis on writing seemed to make kids better writers, better readers, and perhaps, better thinkers. What does published research say? Is there any reason to expect that a writing curriculum, if implemented in other schools, would bring the same benefits?
There is, but implementing it correctly is no small matter.
Better writing: Perhaps the least surprising claim is that a focus on writing improves student writing. In general, there is good evidence that explicit teaching of writing makes kids better writers (for a recent review, see Graham et al, 2012). I emphasize explicit because these interventions concerned with the nuts and bolts of writing: instruction in text structure, how to use specific strategies for planning, revising, or editing text, and so on. As Tyre notes, if a teacher does not show students how to construct a paragraph or a well-written argument, some will figure out it anyway, but many will not.
Better reading: A recent meta-analysis (Graham & Hebert, 2011) summarized dozens of studies examining the impact of writing instruction on reading comprehension. The authors concluded that there is a consistent, positive effect, and argued for three classroom practices.
First, more writing. (No surprise there.) Second, having students write about the texts that they read: for example, close analysis and interpretation, summaries, or the answering of questions, all of which demand understanding. Third, explicit teaching of the skills and processes that go into creating text. If students understand the conventions of writing an effective sentence, an effective paragraph, and an effective essay, then they will better understand how authors use those conventions. For example, they will understand that the start of a new paragraph likely signals the start of a new idea.
A writing assignment may guide student thinking toward substantive issues in, say, history, or it may guide students down a mental primrose path.
It's worth noting that these two advantages -- better writing and better reading -- will probably not accrue if most writing assignments consist of answering short questions, writing in journals, and completing worksheets -- exactly the writing tasks on which elementary school kids spend most of their time (Gilbert & Graham, 2010). Students need assignments that include writing in longer formats with some formal structural requirements.
Better thinking: There is a certain logic to the idea that students can become better critical thinkers by completing writing assignments. Writing forces you to organize your thoughts. Writing encourages you to try different ideas and combinations of ideas. Writing encourages you to select your words carefully. Writing holds the promise (and the threat) of a permanent record of your thoughts, and thus offers the motivation to order them carefully. And indeed some forms of writing--persuasive or expository essays for example -- explicitly call for carefully ordering thinking.
The foregoing logical case may be convincing, but the data are not. Efforts to use writing to teach subject matter have had mixed success (Bangert-Drowns, Hurley & Wilkinson, 2004).
That mixed record is likely due to the considerable diversity in how these programs were implemented and how "success" was measured. A writing assignment may guide student thinking toward substantive issues in, say, history, or it may guide students down a mental primrose path. Merely asking students to write about academic content is no guarantee of better learning; it must be a vehicle for students to engage in serious subject-matter work. Unfortunately, a recent survey (Kiuhara et al 2009) indicated that most high school students encounter writing assignments that typically do not demand this sort of analysis.
It's essential to keep this foremost in our minds, because just asking students to write won't teach them how to think if it's not part of a larger plan to ensure that this writing is done in the context of subject matter.
To put it another way, I might assign this writing assignment in a history class: "Consider how World War II might have ended differently if the plot to assassinate Hitler had succeeded." Unless my students already have some solid background knowledge about the War, about German history and culture, I shouldn't be surprised if the essays I get in response aren't much good. Sure, we expect students will conduct research to write the essay, but in the absence of some background knowledge, it's very hard to know where to begin with such research.
And this is why I say that the New Dorp results are likely replicable, but we must pay close attention to what happened there. It's easy to remember only that "they asked the kids to write a lot." But as Tyre describes, they placed an intense emphasis "on teaching the skills that underlie good analytical writing." There was explicit teaching of writing, and the emphasis was on analysis. I would add that this instruction must be paired with substantive content in order to pay dividends in critical thinking.