College teachers devote a great deal of effort to grading students’ papers. We do this not simply to assign grades, but for the more important purpose of giving students feedback that will help them improve their work in the future. We should ask, then, whether grading papers is an effective teaching practice; that is, to what extent do students benefit from the comments we write on their papers? We will report on an examination of this question in the context of mathematics and then allow time for the audience to discuss this question in the context of other disciplines.