Song, Haisheng, and Haiping Xue. 2022. “The Impact of Extracurricular Tutoring Time Investment on Academic Performance of Secondary School Students: An Empirical Analysis Based on PISA2015 Data of Four Provincial Administrative Regions in China”. Science Insights Education Frontiers 11 (2):1551-65. https://doi.org/10.15354/sief.22.or052.