Table 1.
Demographic characteristics of participants (n=1481)
| Variables | n (%) or mean±SD | |
| School areas | Inner urban | 678 (45.8) |
| Peri-urban | 803 (54.2) | |
| Age (median (IQR)) | 16.0 (1.0) | |
| Gender | Boy | 739 (49.9) |
| Girl | 742 (50.1) | |
| Residence | City | 957 (64.6) |
| Village | 524 (35.4) | |
| Only-child status | Yes | 525 (35.5) |
| No | 956 (64.5) | |
| Boarding school | Yes | 859 (58.0) |
| No | 622 (42.0) | |
| Average monthly living expenses (RMB) | Low | 861 (58.1) |
| Medium | 465 (31.4) | |
| High | 155 (10.5) | |
| Father’s educational level | Low | 163 (11.0) |
| Medium | 832 (56.2) | |
| High | 486 (32.8) | |
| Mother’s educational level | Low | 278 (18.8) |
| Medium | 808 (54.6) | |
| High | 395 (26.6) | |
| Academic grades | Top 50% | 945 (63.8) |
| Last 50% | 536 (36.2) |