The Pygmalion Effect, also known as the Rosenthal Effect, refers to the phenomenon of people improving their performance when others have high expectations of them. For students, when teaches expect a lot, students often perform better. This is the Pygmalion Effect and is named after the play, Pygmalion, by George Bernard Shaw.
The opposite of this is the Golem Effect in which people perform worse when others expect little of them. Both of these are forms of Self-Fulfilling Prophecies.