This document discusses labelling and its impact on student achievement. It defines labelling as stereotyping students based on biased perceptions. Teachers inevitably label students, such as viewing working-class students or poorly-behaved students as less bright. This labelling can become a self-fulfilling prophecy, where students internalize the labels and their behavior and performance conform to teacher expectations. The document also summarizes Rosenthal and Jacobson's famous study which found that when teachers were told certain students were high-achievers, even though the labels were random, those students performed better due to increased teacher attention and expectations.