What is Best for Students, Numerical Scores or Letter Grades?

TL;DR

This paper models and compares the motivational effects of letter grading schemes versus numerical scores on students, revealing conditions where each approach can be more effective for student performance.

Contribution

It introduces the first model analyzing how grading schemes impact student motivation and performance, providing theoretical and experimental comparisons between uniform letter grades and numerical scores.

Findings

Numerical scores can outperform uniform letter grades under certain realistic conditions.

Uniform letter grading schemes may sometimes be more motivating than pure numerical scores.

Experimental results support the theoretical analysis, showing cases where each scheme is preferable.

Abstract

We study letter grading schemes, which are routinely employed for evaluating student performance. Typically, a numerical score obtained via one or more evaluations is converted into a letter grade (e.g., A+, B-, etc.) by associating a disjoint interval of numerical scores to each letter grade. We propose the first model for studying the (de)motivational effects of such grading on the students and, consequently, on their performance in future evaluations. We use the model to compare uniform letter grading schemes, in which the range of scores is divided into equal-length parts that are mapped to the letter grades, to numerical scoring, in which the score is not converted to any letter grade (equivalently, every score is its own letter grade). Theoretically, we identify realistic conditions under which numerical scoring is better than any uniform letter grading scheme. Our experiments confirm that this holds under even weaker conditions, but also find cases where the converse occurs.