David Harding's theory of cultural heterogeneity (2010) seeks to amend existing theories of neighborhood mechanisms, such as social isolation and social organization theories, by (re)introducing a cognitive view of culture that allows for individual agency, divergent outcomes, and influence of conventional or mainstream cultural models. Constructed based on interviews, Harding's theory of cultural heterogeneity has yet to be tested using quantitative methods. After operationalizing cultural heterogeneity, I use nationally representative data from the National Longitudinal Study of Adolescent Health and multilevel mixed-effects logistic regression to test the effect of cultural heterogeneity on the probability of graduating high school, a common measure of educational attainment. My results suggest that cultural heterogeneity does have an effect on educational attainment, but not in the direction specified by Harding's theory. Further research is needed to conceptually clarify cultural heterogeneity in an effort to construct a better operationalization of the theory.