The Role of Shadow Education in the Process of Generating Educational Inequality: An Approach Using Causal Decomposition Analysis

This study aims to clarify shadow education's role in generating educational inequality using a new statistical approach called causal decomposition analysis. Shadow education, such as cram schools and private tutoring, was once a unique educational phenomenon in East Asia but has now spread worldwide (Park et al. 2016). In the sociology of education, shadow education has been positioned as a mechanism that exacerbates educational stratification by conferring advantages on already privileged students (Buchmann et al. 2010). On the other hand, recent research focusing on the causal effect of shadow education has demonstrated the heterogeneous effect that shadow education has more significant effects in disadvantaged groups (Choi and Park 2016). This result suggests that shadow education potentially has the function of reducing disparity as an equalizer. However, prior studies have independently examined the relationship between social origin and shadow education participation and between the use of shadow education and educational attainment. Therefore, it has not been able to directly examine how much shadow education contributes to the generation of educational inequality. Therefore, in this study, we use a novel causal decomposition analysis and a double machine learning technique rising in recent studies on inequality and health disparity to directly examine how much equalizing opportunities for shadow education among the social classes reduces the educational achievement gap among the social classes and how much of the gap remains. The results of the analysis using the SSM 2005 and 2015, Japan's national representative data, showed that even if opportunities for shadow education were equalized, the gap in educational achievement would not be significantly reduced. This result suggests that shadow education is neither a stratifier that increases educational inequality nor an equalizer that reduces it.