Some educators highlight striking similarities between writing and learning. From this point of view, to engage students in writing activities about content is to engage students in learning that content. Among the benefits of more frequent writing, it is argued, would be better retention and understanding of subject matter content. Writing requires the active organization of personal understandings. The externalization of those understandings in symbolic form makes them available for feedback in self-reflection and revision, in review of a record of the evolution of ideas and understanding, and in documentation for public discourse.
Alternatively, some researchers have cautioned that the educative effects of writing may be contingent on the contexts in which it occurs. The research on writing’s effects on learning is ambiguous. A meta-analysis by Bangert-Drowns, Hurley, and Wilkinson attempts to shed more light on the question of what the effects of writing on learning really is.
In their meta-analysis they included 48 school-based writing-to-learn programs. These programs involved different grade levels, different subject matter, different kinds of writing assignments, and different durations of treatment.
The mean effect of writing-to-learn interventions on content achievement was rather small but significantly greater than no effect. In fact, 36 of 48 study outcomes (75%) were positive, suggesting a fairly consistent positive achievement effect attributable to writing-to-learn interventions. The average weighted Cohen’s d was 0.17 standard deviations.
There were also factors which mediated the effect of writing-to-learn interventions on achievement. The ones of most interest are minutes per in-class writing task (with longer tasks showing a relatively weaker effect), the presence of metacognitive prompts (which increases the effect of writing on learning), and the length of the writing-to-learn training program (with longer programs showing a stronger effect). Both of these showed strong relations with effect size of writing-to-learn achievement effects. Surprisingly, the presence of feedback did not affect the relationship between writing-to-learn and achievement.
In short: there is good evidence that writing-to-learn has a small, but noticeable effect on students' achievement. Ideally, students receive high quality metacognitive prompts to aid their writing, and have to write often (but not too long at a time).
Bangert-Drowns, R. L., Hurley, M. M., & Wilkinson, B. (2004). The effects of school-based writing-to-learn interventions on academic achievement: A meta-analysis. Review of educational research, 74(1), 29-58.