The enrollment rate of high schools and pupil-teacher ratio in middle schools have become increasingly important to measure the level of education development in China. This paper tries to study the impacts of the pupil-teacher ratio on students’ high school enrollment rate. Specifically, I examine the association between pupil-teacher ratio and enrollment rate using data from 2013 to 2020 to understand the transformation of China’s education system. I first document a significant negative correlation between the two variables, which indicates that a decreasing pupil-teacher ratio would have a positive effect on the high school enrollment rate. To address the endogeneity issue, I use the provincial governor’s working experience in the education sector as an instrumental variable. By using 2SLS, I find a larger positive effect of the expanded supply of teachers on the high school enrollment rate. The results confirm the essential role which the pupil-teacher ratio has played in improving education quality.