Pygmalion effect
expectation lifts achievement
Today this word meansThe phenomenon in which the expectations placed on someone actually raise their achievement.
Named for Pygmalion, whose beloved statue became a living person.
It took hold with the 1968 study in which Rosenthal and Jacobson told teachers "these children will grow remarkably," then observed real changes in their grades.
The opposite direction — low expectations dragging achievement down — is called the golem effect.