Teachers' expectations about their students' abilities affect classroom interactions in myriad ways that can impact student performance. Students expected to succeed, for example, get more time to answer questions and more specific feedback.
"The first psychologist to systematically study this was a Harvard professor named Robert Rosenthal, who in 1964 did a wonderful experiment at an elementary school south of San Francisco.
The idea was to figure out what would happen if teachers were told that certain kids in their class were destined to succeed, so Rosenthal took a normal IQ test and dressed it up as a different test."
Via Gina Stepp