The purpose of present study was to evaluate the effects of peer support program on children's school adjustment. Japanese children from third-grade to sixthgrade (n=710 by 2010 year, and n=950 by 2011 year) from 5 schools were given the peer support program. The control group (Japanese children from third-grade to sixth-grade (n=478 from 4 schools by 2010 year, and n=400 from 3 schools by 2011 year)) received no specific instruction. They completed a questionnaire about Adaptation Scale for School Environments on Six Spheres. The results indicated that children receiving peer support program performed significantly higher on some factors. These results suggest that peer support program is likely to make children be better adjusted to school. In order to make peer support program more effective, the practice combined with SEL (Social and Emotional Learning) and Collaborative Learning based on CSGCP (Comprehensive School Guidance and Counseling Program) is required.