Abstract: In recent decades, with the rapid marketization of educational resources in K-12 education, private tutoring has become widely popular in China, Yet, previous research has not reached a consensus on the impact of private tutoring on academic outcomes, and has also overlooked the influence of individuals' choice under Chinese exam-oriented educational system. By using data from the China Education Panel Study (CFPS), this study examines the heterogeneous treatment effects of private tutoring on eighth graders' academic performance from the perspective of individual choices. The results show that propensities to participate in private tutoring can differentiate the class disparities among middle school students in terms of their individual, family, school and other parenting factors. Furthermore, the results indicate that private tutoring on average has limited impacts on academic achievement, net of all background factors. However, students whose propensities to participate in private tutoring is in the middle range tend to benefit the most from private tutoring. For both the students of socioeconomically disadvantaged families with low propensities and their advantaged counterparts with high propensities, private tutoring has little effect on their academic performance. Sensitivity analysis further shows that the heterogeneous effects of private tutoring differ in cognitive ability, subject types, and tutoring periods. The finding carries out important implications for understanding the consequences of China's policy interventions in reducing educational inequality.

Key words: private tutoring, self-selection, heterogeneous treatment effects, marketization of education, educational equality