Another great suggestion from Nick Carbone, via Techrhet.

lau and Caspi learned two things: first, that in general students felt that collaborating with partners improved the quality of drafts. On the other hand, the students mostly felt that their edits improved other people’s drafts, whereas other people’s edits worsened their own drafts. Blau and Caspi posit that a sense of ownership of the draft was pedagogically useful–that students’ perceptions of the overall quality of their work increased as they felt responsible for it. As a consequence, they conclude that the best way to reap the benefits of collaboration and psychological ownership of writing is to have students make suggestions to one another’s drafts, but not to edit one another’s writing directly. —Collaboration and Ownership in Student Writing – ProfHacker – The Chronicle of Higher Education.

Like most writig teachers, I do encounter occasional resistance to peer collaboration assignments, so I will have to look more closely at the original study. I typically have journalism students copy-edit each other’s near-final drafts, in large part because the student editors will be responsible for copy edits anyway if the student writers submit the article to the school paper. But copy editing is not the same thing as rewriting.