Grade-equivalent scores are widely used in the school system in reporting students' performance on standardized achievement tests. This paper explores how grade equivalent scores are calculated and interpreted. In addition, the paper examines the limitations of grade-equivalent scores through the use of small heuristic data sets. A grade-equivalent score is a score indicating the grade level at which this score is the mean performance level. They are created by administering a test to students in various grades. Typically, a test being normed is administered to large groups of students in each of several successive grade levels at different times of the year. Grade norms have several limitations and are often misinterpreted. It must be noted that when grade-equivalent scores are derived, it does not mean that the test was given to all grades or to children at all different points on a grade's continuum. Grade-equivalent scores reported beyond tested grade limits can be misleading. In addition, grade-equivalent scores obtained from tests produced by different publishers often give conflicting results. A further limitation is that grade-equivalent scores should not be used to make comparisons of the grade-equivalent performances of an individual across different subjects. Other incorrect interpretations are reviewed. (Contains one table, three figures, and nine references.) (SLD)