Because the portfolio system requires that you analyze and reflect on your own writing processes and growth as writers, you are positioned to assume responsibility for the quality of your work. Students learn to become independent writers and learners rather than relying on the instructor for approval and direction. Portfolios contain a range of work and therefore let you come to see yourselves as authors who write differently for different audiences or who make distinctive choices about how you convey information. As implied, you can investigate how your own revising or editing skills change over time. Since your pieces don't disappear after the first few drafts, you can afford to let ideas incubate and take enormous trouble over the small changes that distinguish a third draft from a handsomely crafted final work.
Instructors also benefit from the portfolio system.
Because scoring portfolios requires teachers to meet in small, working groups to discuss assignments, set standards, and select writing samples, it also encourages collaboration among instructors and the sharing of successful teaching strategies. By this exchange, instructors are able to improve the quality of the total writing program as well as their individual effectiveness in the classroom. The portfolio system enables the instructor of a writing class to become a coach and editor rather than simply a judge, collaborating with the student by providing feedback and helping the student learn to get help from others with his or her writing. The portfolio system encourages instructors to focus on specific aspects of writing and to develop responsive skills in students. Instructors and students confer and discuss reactions to writing rather than debating grades, thereby establishing a writing environment rather than a competitive environment in the classroom.