This study examined whether having African-American middle school students write essays affirming their personal values improved their academic performance.
Among African-American students, completing writing exercises about their values increased their average seventh- and eighth-grade GPA by a quarter of a letter grade (0.24 points), a change that was statistically significant. The intervention did not have a statistically significant effect on the academic outcomes of European-American students.
Cohen, G. L., Garcia, J., Purdie-Vaughns, V., Apfel, N., & Brzustoski, P. (2009). Recursive processes in self-affirmation: Intervening to close the minority achievement gap. Science, 324(5925), 400–403.