I've found it a rather useful way of thinking about the misbehaviour of students in the Middle Ages, the topic of my current research project. These students were constantly being stereotyped by those around them as noisy, drunken, brutal and sexually immoral. And certainly a noisy minority behaved in precisely such a way. But surely this misbehaviour was shaped by the fact that the perpetrators knew that they were being constantly categorised as deviant. In a sense, the choice of behaviours open to them was limited by the railing of preachers, parents, chroniclers and so on. And sometimes, the students responded in quite explicit ways to the stereotypes. My favourite example is a naughty student who signed off a letter requesting money from his guardian with the words 'From one who eats well, drinks better and sleeps the best': he was cleverly mixing the negative stereotypes with the language used to describe a model student. We can then begin to analyse the particular gestures of naughty students by thinking about how they might, ironically, have been encouraged in their often very imaginative use of violence, by the very comments which sought to condemn it - they seemed often to take a certain pride in their actions.
I was therefore particularly interested to read in The Spirit Level that stereotyping students and children has been shown to directly affect their academic performance: they cite a study by Jane Elliott, a schoolteacher in the 60s, who told her students that it was scientifically proven that blue-eyed children were more likely to succeed than their lazy brown-eyed counterparts - sure enough, the children then fulfilled this prophecy in the test she set them; when she then informed them that she'd got the thing muddled up, and actually it was blue-eyed children who were lazy, the results dramatically reversed. Wilkinson and Pickett comment that 'When we expect to be viewed as inferior, our abilities seem to be diminished' (p. 113).
The effects of stereotyping can't explain all underachievement and misbehaviour, but the historical evidence, as well as these more recent sociological studies, indicate that the ways in which talk about others carry a big responsibility.