As private tutoring becomes globally widespread, many worry that an expansion of private tutoring aggravates educational inequality and ultimately intergenerational mobility. We address the issues by estimating the average and distributional effects of private tutoring on academic outcomes of Korean middle school students. Applying a semiparametric model recovering distributions in difference-in-differences models, we discover that the presence of private tutoring shifts the upper half of the outcome distribution rightward, but it exerts statistically insignificant effects on the lower half of the distribution. Our result suggests that the expansion of private tutoring in an education system is expected to aggravate educational inequality more than an empirical method reporting modest average effects suggests.