Control Variables

The control variables consist of covariates at student level and school level. Regarding control variables at student level, the index of reading diversity was 0.44, while the index of online reading was −0.35. The low index of online reading indicated that Shanghai 15-year-old students had less opportunity to read online than their counterparts in OECD countries. Girls accounted for 51.25%. The majority of 15-year-old students were from general middle schools (40.92%), followed by general high schools (37.99%), upper secondary vocational schools (20.41%), and 6/7-year secondary vocational schools (0.68%). Students born in Shanghai accounted for 84.47% of the total, followed by 14.56% born in other provinces, 0.23% born in Hong Kong, Macau, or Taiwan, and 0.74% born in foreign countries. Family characteristics included socioeconomic status and family structure. Socioeconomic status was measured by the variable “SES,” whose mean (−0.48) was lower than the OECD average (0). Students from two-parent family, single-parent family, and other family structure accounted for 86.59%, 10.60%, and 2.81%, respectively. Control variables at school level included school type, school resources, school size, student–teacher ratio, teacher quality, teacher participation, school average SES, and school climate. Private schools accounted for 10.23% of all schools. The means of shortage of teaching staff and quality of educational resources were 0.57 and 0.15, respectively. The school size was 1,660 and the student–teacher ratio average was about 14. About 14.97% of teachers had teaching certification. Teacher participation in decision making (0.86) was higher than the OECD average. The school average SES was −0.48. School climate measured by student factors such as student absenteeism was 0.10.