Writing-to-learn (WTL) activities take very little class time, and most teachers find they can give a quick WTL prompt at the beginning of class while they take roll and as students are settling in. Moreover, many WTL activities can be limited to just a minute or two--the amount of time it might take to answer a student's question about a course concept. Also, because WTL activities are such valuable learning tools, most teachers feel that students use any minutes given over to WTL writing very effectively.
If you decide to give a disciplinary writing assignment (a formal document that students work on over a long period and revise before submitting it for grading), then peer review is an excellent way to assure that students are revising. One way to save class time is to require students to do their peer review as homework outside of class. They will appreciate having class time for peer review, but you can either require that they meet to read, comment on, and discuss each other's draft or that they exchange drafts at the end of one class and return drafts and peer review sheets at the beginning of the next class.
If you decide to require out-of-class peer review, you might want students to contact each other and exchange drafts through e-mail. If so, consider referring them to our Writing@CSU guide on e-mail. It includes information about e-mail etiquette as well as attaching lengthy files.