Cognitive and social-emotional development in the first three years of life is associated with later skills. However, little is known about the paths of developmental delays in both cognitive and social-emotional skills before age 3 or to what extent these paths predict later developmental outcomes. The aim of this study is to examine the associations between the different paths of developmental delays in both cognitive and social-emotional skills of children before age 3 and the levels of development of the children when they are preschool age. Using a longitudinal data collected at three time points from 1245 children and their caregivers in rural China, we identified four different paths of developmental delays in cognitive and social-emotional before age 3 and examined how these paths are associated with different levels of developmental outcomes at preschool age. We used a non-parametric standardization approach and an ordinary least squares model to perform our analyses. Findings show that rates of developmental delays in either cognitive or social-emotional domain or both domains are high at all different time points, ranging from 20% to 55% for cognitive delays and 42% to 61% for social-emotional delays. Over half of children experienced deteriorating levels of either cognitive or social-emotional development before age 3. A large share of children was found to be persistently delayed in either domain. Only a small share of children raised their levels of development in either domain before age 3. In addition, we identified certain socioeconomic status of the family that are associated with never or deteriorating path of child developmental delays. More importantly, we revealed that different paths of developmental delays before age 3 have predictive power on different levels of developmental outcomes at preschool age. Our results suggest that actions are needed at the earliest times to improve child development when children are still infants or toddlers.

Background: The association between sleep patterns and young students’ mental health, which is crucial for their development, remains understudied in rural China. Therefore, the relationship between sleep patterns and mental health among primary and junior high school students in rural China was examined. Method: A total of 1592 primary and junior high school students from rural areas of Gansu Province were surveyed, and the Depression Anxiety and Stress Scale (DASS) was utilized to assess mental health, alongside self-reported data on their daily sleep patterns. Results: Significant sleep inadequacies were identified: 28% of students received less than 8 h of sleep on weekdays, and 19% went to bed later than recommended. On weekends, 38% of students had delayed bedtimes, though only 7.2% received less than 8 h of sleep. Notably, a “U-shaped” relationship was uncovered between sleep duration and mental health for students on weekends, with optimal mental health correlated with receiving 10–11 h of sleep, while both shorter and longer sleep durations on weekends worsened outcomes. This pattern is absent on weekdays. Additionally, adequate sleep and an earlier bedtime was linked to a 6–8% decrease in mental health risks. Conclusions: These findings provide valuable insights for policymakers seeking to enhance student mental well-being in rural settings, emphasizing the importance of implementing measures that promote balanced sleep habits among young students.

Background
Comorbidity in mental disorders is prevalent among adolescents, with evidence suggesting a general psychopathology factor (“p” factor) that reflects shared mechanisms across different disorders. However, the association between the “p” factor and protective factors remains understudied. The current study aimed to explore the “p” factor, and its associations with psycho-social functioning, in Chinese adolescents.

Methods
2052 students, aged 9–17, were recruited from primary and secondary schools in Shanghai, China. Multiple rating scales were used to assess psychological symptoms and psycho-social functioning. Confirmatory factor analysis was conducted to verify the fit of models involving different psychopathology domains such as externalizing, internalizing, and the “p” factor. Subsequently, structural equation models were used to explore associations between the extracted factors and psycho-social functioning, including emotion regulation, mindful attention awareness, self-esteem, self-efficacy, resilience, and perceived support.

Results
The bi-factor model demonstrated a good fit, with a “p” factor accounting for 46 % of symptom variation, indicating that the psychological symptoms of Chinese adolescents could be explained by internalizing, externalizing, and the “p” factor. Psychologically, a higher “p” was positively correlated with emotion suppression and negatively correlated with mindful attention awareness, emotion reappraisal, self-esteem, and resilience. Socially, a higher “p” was associated with decreased perceived support.

Limitations
Only common symptoms were included as this study was conducted at school. Furthermore, the cross-sectional design limited our ability to investigate causal relationships.

Conclusions
A “p” factor exists among Chinese adolescents. Individuals with higher “p” factor levels were prone to experience lower levels of psycho-social functions.

Policymakers in China have attempted to improve the quality of rural education by investing in teacher salaries through initiatives like the Rural Teachers Support Plan (RTSP). This study estimates the effects of teacher salary increase on students' educational outcomes in rural China by utilizing the exogenous variations of rural teacher salaries induced by the RTSP. It employs an intensity-based difference-in-differences strategy and panel data from 2010 to 2018 with 3,351 rural children. The findings reveal that an increase in teacher salaries had a significant positive impact on students' examination results. Moreover, the results of mechanism analysis indicate that salary increases could have both quality and quantity effects on students' outcomes by increasing the proportion of highly educated teachers and reducing the student–teacher ratio. Our findings contribute to the discussion on the importance of teacher salary incentives in education production functions and provide insights for other countries undertaking rural education reforms.

Rural girls in China stay in school longer than boys and outperform them in many subjects. This gender gap suggests analogous disparities in early childhood development, a key factor in later educational outcomes. This study examines gender disparities in social-emotional development among 1,301 children aged 18–30 months in rural China. Results indicate that male children trail their female counterparts by 0.18 SD on average on the scale of standardized ASQ:SE score. A large share of the difference is driven by the bottom 10 % of children, where the magnitude of the gender gap (0.34 SD) is 1.9 times larger than at the median (0.19 SD). Demographic characteristics are uncorrelated with the gender gap in heterogeneity analysis, suggesting that the mechanisms underlying observed gender disparities are similar across rural Chinese households.