2.1. Study Design and Participants
This study was embedded within the DECIDE-Children study. Using the cluster random method and stratified by district (urban or suburban), 24 schools (8 schools in each region) were divided in a 1:1 ratio into the intervention group or control group, involving 1392 eligible children aged 8 to 10 years. A researcher at the Clinical Research Institute of Peking University, who was blinded to the schools, was in charge of the randomization process. The study was reviewed and approved by Peking University Institutional Review Board (IRB00001052–18021), and the informed consent of all children and parents was obtained before their participation in the study.