This meta-analysis summarizes empirical results on the correspondence between teachers' judgments of students' academic achievement and students' actual academic achievement. The article further investigates theoretically and methodologically relevant moderators of the correlation between the two measures. Overall, 75 studies reporting correlational data on the relationship between teachers' judgments of students' academic achievement and students' performance on a standardized achievement test were analyzed, including studies focusing on different school types, grade levels, and subject areas. The overall mean effect size was found to be 0.63. The effect sizes were moderated by use of informed versus uninformed teacher judgments, with use of informed judgments leading to a higher correspondence between teachers' judgments and students' academic achievement. A comprehensive model of teacher-based judgments of students' academic achievement is provided in the Discussion. (Contains 3 tables, 1 figure and 4 footnotes.)