An article in the Sept. 1 issue of Science by Cohen et. al. and an accompanying review by Wilson point out the power of brief interventions that change people's self- and social perceptions.
You may... "undoubtedly be surprised, or even incredulous, that a 15-min intervention can reduce the racial achievement gap by 40%. Yet this is precisely what Cohen et al. .... African American seventh graders randomly assigned to write about their most important values achieved significantly better end-of-semester grades than students in a control condition. How can this be?"
The table shows the result of this and similar studies (click to enlarge):
Legend: Brief theory-based interventions improved students' grades [increases shown on a four-point grade point average (GPA) scale, relative to randomly assigned control groups].
"The Cohen et al. study and the others like it illustrate key social psychological points. It can be as important to change people's "construals"--their interpretations of the social world and their place in it--as it is to change the objective environment....It is not clear why students in the Cohen et al. sample failed to self-affirm on their own. Why did it take an in-class essay to focus students' attention on values that were important to them? Issues of generalizability also arise, such as whether the self-affirmation exercise would work with younger age groups."