Bias or discrimination in teacher evaluations can affect student academic outcomes such as self-confidence, academic motivation, effort, and achievement. This study examines the impact of perceived discrimination on student performance and classroom communication. The lab-in-the-field experiment, conducted among 9th- and 11th-grade students in upper secondary schools in Hungary, involves five rounds of an effort task followed by randomly assigned fair, unfair, or discriminatory feedback and communication through pre-programmed messages. Hypotheses 1 and 2 propose that students exposed to discrimination will demonstrate lower performance and an increased likelihood of expressing disinterest in the task compared to their peers in the control group. Data will be collected during February 2024 with a target sample size of approximately 1000 respondents from diverse backgrounds. The design and hypotheses have been pre-registered with OSF Registries. The results of this study have potential implications for understanding the behavioural and academic consequences of discriminatory treatment in educational settings.