Grades tend to reduce the quality of students’
thinking. Given that students may lose interest in what they’re learning as
a result of grades, it makes sense that they’re also apt to think less
deeply. One series of studies, for example, found that students given
numerical grades were significantly less creative than those who received
qualitative feedback but no grades. The more the task required creative
thinking, in fact, the worse the performance of students who knew they were
going to be graded. Providing students with comments in addition to a grade
didn’t help: the highest achievement occurred only when comments were given
instead of numerical scores (Butler, 1987; Butler, 1988; Butler and Nisan,
1986).