* Self-fulfilling prophecy: This is the most likely conclusion. The teacher's high expectations create a positive feedback loop. The teacher provides more attention, encouragement, and challenging opportunities to these students, leading to increased effort and achievement. This confirms the teacher's initial expectations, reinforcing the cycle.
* Teacher bias (conscious or unconscious): The teacher might be unconsciously biased towards students who remind them of themselves, or who exhibit certain characteristics (e.g., socioeconomic status, race, demeanor) that the teacher associates with success. This bias could manifest in subtle ways, such as giving more positive reinforcement or providing more opportunities to participate.
* Tracking and ability grouping: The school might have a system of tracking or ability grouping, where higher-achieving students are placed in more advanced classes or receive specialized instruction. This could lead to a self-selective effect, where high-achieving students are more likely to be in the teacher's class in the first place.
* Socioeconomic factors: Students from more affluent backgrounds might receive more support at home, leading to higher achievement. If the teacher also expects more from these students (perhaps unconsciously), it could reinforce the existing socioeconomic disparities.
* Student self-perception: High expectations from a respected authority figure (the teacher) might boost the students' self-esteem and confidence, leading them to strive for higher achievement. This is related to the self-fulfilling prophecy but emphasizes the student's agency in the process.
It's important to note that these factors are not mutually exclusive; several might be operating simultaneously. A sociologist would likely conduct further research to determine the relative importance of each factor in explaining the observed correlation. Simply observing the correlation doesn't prove causality.