This paper is a synthesis of research completed over the last 100 years answering the central research question, “What do grades mean?” The compilation uncovers the degree to which grades serve as a useful educational measure. The grades that teachers assign to student work vary greatly, and this variation has persisted over the past century due to multiple factors. Over the past 100 years, research studies repeatedly demonstrate only a moderate correlation between grades and academic measures on standardized tests. Grades typically indicate non-cognitive habits, such as persistence and effort, more strongly than academic knowledge.
The paper details factors in grading variation; the utility of grades as they are presently assigned; and possible methods of improving the reliability of grades as an educational progress metric. It also calls for further research into grading correlations with standardized test scores and academic performance.