The main purpose of this study was to explore the relation between teacher expectations and student achievement in physical education classes, in the light of three complementary hypotheses. Student achievement may confirm teacher expectations because these expectations create self-fulfilling prophecies, create perceptual biases, or accurately predict, without influencing, student achievement (Jussim, 1989). Another purpose was to examine the mediating role played by student perceived ability in the teacher expectancy process. Study data were obtained from 173 students and 7 teachers. Path analysis revealed that teacher expectations have weak self-fulfilling effects, strongly predicted student achievement mainly because they are accurate, and have no biasing effects on teacher judgements. Results also bring evidence concerning the role of partial mediator of student perceived ability in the confirmation process of teacher expectations.