In this study we use data from the Early Childhood Longitudinal Survey third- and fifth-grade samples to investigate teacher judgments of student achievement, the extent to which they offer a similar picture of student mathematics achievement compared to standardized test scores, and whether classroom assessment practices moderate the relationship between the two measures. Results indicate that teacher ratings correlate strongly with standardized test scores; however, this relationship varies considerably across teachers, and this variation is associated with certain classroom assessment practices. Furthermore, the evidence suggests that teachers evaluate student performance not in absolute terms but relative to other students in the school and that they may adjust their grading for some students, perhaps with basis on perceived differences in need and/or ability. (Contains 9 tables, 2 figures and 5 footnotes.)