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.