"If we ask students to articulate in clear writing what they are studying, we help ensure that they will in fact learn it. And without these carefully written essays and essay exams, we can’t give trustworthy final course grades – grades that reflect whether students actually understand what we want them to understand” (Elbow and Sorcinelli, 2011, p. 213).

Elbow and Sorcinelli also distinguishes between low-stakes writing and high-stakes writing.

Low-stakes writing is more informal, comfortable, and exploratory. Students could be asked to reflect on a topic for a few minutes in class or outside class. In contrast, high-stakes writing is directly related to grades and has to be clear and comprehensible. For best results, topics have to be of interest to the student, evaluation criteria has to be clearly communicated, and students should have the opportunity to submit drafts and get feedback.

Source: McKeachie’s Teaching Tips: Strategies, Research, and Theory for College and University Teachers, Svinicki, M, McKeachie, WJ, 2011