The teacher's task of assigning letter grades to students and the public's interpretation of them can be perplexing. Does the student's grade represent the level of achievement, the gain in achievement, or some combination of the two? Is the student's effort included in the grade, or are high achievers given good marks regardless of effort? Are pupils marked according to their own potential learning ability or in relation to their classmates' achievement? There are no clear answers to these questions. Despite attempts at precise directives, practices tend to vary by school, teacher, and context. Scores on an FCAT standardized test seem to be a different matter. Such tests are designed to be criterion-referenced, intending to determine whether a student has mastered the material taught in a specific grade or course. The apparent objectivity of the test and its connection to a specific curriculum gives the impression of a pure measure of student achievement. But tests, no matter how carefully designed, are inevitably imperfect and measure only a sample of student behavior over a very short period of time. What exactly do classroom grades represent in Miami-Dade schools and what is their relationship to FCAT scores? How is it that some students can get very high classroom grades and still score at below-proficiency levels on the FCAT? What should educators expect the relationship to be between classroom grades and FCAT scores? These and other issues regarding grades and test scores are explored in this paper.