Whichever grading method is used, it is important that students always get some sort of written comment, no matter how brief, in addition to the grade. Not only does the comment help students understand their grades, it reminds them that there is an actual human audience for their writing, with whose responses they should be concerned. Most importantly, the comment gives students suggestions for future improvement, and so is essential to their development as writers. Comments should explain or justify the grade assigned, and should suggest ways the student might improve that grade next time around. For this reason, they are also useful to the instructor: in the event that a student questions a grade, the comment can remind you of your reasons for assigning it.
Several different types of comments may be appropriate in responding to student writing:
You may want to draw the student's attention to sentence level errors which mar the appearance of the paper or distract the reader. It is especially useful to point out errors the student makes repeatedly, for by correcting such errors students may be able to greatly improve the appearance of their writing.
It is not necessary-and may even be a bad idea-to mark all errors. A student who gets back a paper which has been "defaced" (or "bloodied," if you mark in red pen) with numerous teacher's corrections may feel too discouraged by the enormity of his or her problems to attend to them. Pointing out two or three of the most significant corrections that need to be made might be more effective.
Often, instructors themselves are not sure how to label or explain an error: the sentence just sounds clumsy or wrong. In such cases it is sufficient to draw the student's attention to the sentence and suggest that he/she consider simplifying it or rewriting it for greater clarity. The instructor can direct students to the Writing Center for detailed explanations.
Brief marginal comments, noting good points or questions raised by specific passages in the paper, are a good way of reminding students that someone is in fact reading and responding to what they have written, and that they need to imagine how readers will respond throughout the paper. The margins are a good place to say something nice (e.g., "interesting idea"), especially in a paper which may have significant weaknesses.
In large classes instructors may legitimately feel they do not have time to make detailed responses to each paper. However, some such response from the teacher is absolutely necessary for the writing assignment to fulfill its educational potential for the student. End comments may be brief, but they should do the following:
Explain and justify the grade: Your comment should make clear to the student in what ways the paper succeeded and in what ways it failed, and how that level of success compares to your expectations of students in the class. Note that if grades are defined in class or on the syllabus (as they are in the Catalog), this explanation will be easier to make.
Try to say something positive: On most papers, students who have made a sincere effort do something right. Try to include some praise in the comment. Positive feedback is as important as negative, and when a student does something that works well it should be pointed out to them.
Always try to suggest some improvement or alternative: By the same token, no paper is perfect, and even very good writers can improve. If you can't think of ways to make the paper better, at least suggest alternatives the author might have considered.
Frame negative comments as suggestions for improvement: Rather than saying "This paper is incoherent," suggest "Your argument might be easier to follow if you treated each of your reasons for believing that the earth is flat in separate paragraphs" or "Next time you might state your argument first and then refute your opponents' arguments."
Limit your comments to the 2 or 3 most important things the student should learn from this paper. Don't overwhelm the student (or yourself) by trying to mention everything the student did right or wrong. Instead, focus on a few important features of the paper, offering a few feasible suggestions for improving performance on the student's next writing assignment.