Research proves that children can perform better if teachers expectation of them is higher

Robert Rosenthal and Lenore Jacobson's study showed that, if teachers were led to expect enhanced performance from children, then the children's performance was enhanced. This study supported the hypothesis that reality can be positively or negatively influenced by the expectations of others, called the observer-expectancy effect. Rosenthal argued that biased expectancies could affect reality and create self-fulfilling prophecies.

All students in a single California elementary school were given a disguised IQ test at the beginning of the study. These scores were not disclosed to teachers. Teachers were told that some of their students (about 20% of the school chosen at random) could be expected to be "intellectual bloomers" that year, doing better than expected in comparison to their classmates. The bloomers' names were made known to the teachers. At the end of the study, all students were again tested with the same IQ-test used at the beginning of the study. All six grades in both experimental and control groups showed a mean gain in IQ from before the test to after the test. However, First and Second Graders showed statistically significant gains favoring the experimental group of "intellectual bloomers". This led to the conclusion that teacher expectations, particularly for the youngest children, can influence student achievement. Rosenthal believed that even attitude or mood could positively affect the students when the teacher was made aware of the "bloomers". The teacher may pay closer attention to and even treat the child differently in times of difficulty.

Rosenthal predicted that elementary school teachers may subconsciously behave in ways that facilitate and encourage the students' success. When finished, Rosenthal theorized that future studies could be implemented to find teachers who would encourage their students naturally without changing their teaching methods. The prior research that motivated this study was done in 1911 by psychologists regarding the case of Clever Hans, a horse that gained notoriety because it was supposed to be able to read, spell, and solve math problems by using its hoof to answer. Many skeptics suggested that questioners and observers were unintentionally signaling Clever Hans. For instance, whenever Clever Hans was asked a question the observers' demeanor usually elicited a certain behavior from the subject that in turn confirmed their expectations. For example, Clever Hans would be given a math problem to solve, and the audience would get very tense the closer he tapped his foot to the right number, thus giving Hans the clue he needed to tap the correct number of times. 

A major limitation of this experiment was its inability to be replicated well. "Most studies using product measures found no expectancy advantage for the experimental group, but most studies using process measures did show teachers to be treating the experimental group more favorably or appropriately than they were treating the control group...because teachers did not adopt the expectations that the experimenters were attempting to induce, and/or because the teachers were aware of the nature of the experiment."

Extracted from Wikipedia