To gain insight into how teachers’ judgment accuracy can be improved, we investigated effects of cue-type availability. While thinking aloud, 21 teachers judged their fourth grade students’ (n = 176) decimal magnitude understanding. Sensitivity (correctly judging what students did understand) did not improve from availability of both answer cues (students’ answers to prior practice problems) and student cues (knowledge of students triggered by knowing their names), and was lower when only answer cues were available, compared to only student cues. Specificity (correctly judging what students did not understand) was higher when only answer cues were available, compared to only student cues or both student and answer cues