"Teacher expectations are inferences that teachers make about present and future academic achievement and general classroom behavior of students (either the entire class or specific individuals). General expectations include teachers' beliefs about the changeability versus the rigidity of students' abilities, the students' potential to benefit from instruction, the appropriate difficulty of material for the class or for a subgroup, and whether the class should be taught as a group or individually. Expectations for individual students may be based on student record information (test data, past grades, comments by previous teachers), knowledge about the family, or initial contact with the student in the classroom (apparent motivation, attentiveness and contributions to lessons, general work habits). Willis (1972) has shown that contact with students leads to the formation of stable (and largely accurate) differential expectations within a few days after the school year begins. Her study (described in detail in Brophy & Good, 1974) illustrates that formation of expectations is normal and is inherently neither good nor bad. The critical issues are the accuracy of the expectations and the flexibility with which they are held. Inaccurate expectations will do damage if teachers not only do not correct them but begin to base instructional decisions on them.
"Expectations tend to be self-sustaining. They affect both perception, by causing teachers to be alert for what they expect and less likely to notice what they do not expect, and interpretation, by causing teachers to interpret (and perhaps distort) what they see so that it is consistent with their expectations. Some expectations persist even though they do not coincide with the facts." (Good, T. L., & Brophy, J. E., 1990, pp. 441-462)