Told a school (California) that they had a new test designed to identify those who would 'spurt' ahead. It was a standard IQ test, but the teachers believed it. The researchers picked 20% of pupils at random; the 'spurters'. A year later, 47% of those identified as spurters made significant progress.
Demonstrates a self-fulfilling prophecy as the teachers accepted that the 'spurters' will spurt ahead by the amount of attention and encouragement given
Rosenthal and Jacobson study is reliable as it has been repeated, but didn't have the same age of pupils and same teaching styles so the original study can't be replicated exactly
Rosenthal and Jacobson study is valid as researchers claimed that teacher's expectations were passed on through differences in the way they interacted with pupils, but later studies found no evidence of this