Which behavioral and visual information do teachers rely on when judging relevant characteristics of their students and which cues should they rely on? Drawing on Brunswik's Lens Model (Perception and the representative design of psychological experiments, University of California Press, 1956. https://doi-org.bibliotheek.ehb.be/10.1525/9780520350519), we investigated the role of students' expression of nonverbal behavioral cues (e.g., friendly facial expression) and physical appearance (e.g., wearing eyeglasses) and how this information is utilized during the judgment process by pre-service teachers and psychology students (N = 102). Perceivers provided ratings of students' (N = 45) academic self-concept, intelligence and motivation in brief nonverbal video clips showing one student each in a physics classroom. Numerous behavioral and physical cues (in total 165) were extracted from the stimulus material by two independent raters. Perceivers achieved highest accuracy for students' motivation, whereas intelligence was judged with the lowest accuracy. Lens model parameter analysis indicated that perceivers strongly relied on students' sex, an attentive and self-assured facial expression, and whether or not a student was wearing eyeglasses in their judgments. Cues that were actually related to students' characteristics, on the other hand, involved students' sex, a masculine and distinctive appearance, and a tensed as well as friendly facial expression. An overall favorable judgment for boys points into the direction of a gender bias. Implications for our understanding of teacher judgment processes and outcomes are discussed.