We have developed a group of school-based universal prevention programs for children's health and adjustment. The programs are characterized by new theories such as the somatic-marker hypothesis and enjoyable methods that utilize animated stories and games. This study adopted one of the programs for the development of self-confidence.

The aim was to examine the effectiveness of the program. In addition to the direct purposes of the program, children's adjustments at school and homeroom class were evaluated as extended effects.

Participants were third grade children in six public elementary schools in Japan. The final sample included 442 children (219 boys and 223 girls). The program was implemented weekly in one regular 45-minute class over 8 weeks. Participants completed a battery of three questionnaires three times, 1 month before the start of the program (T1), 1 week before the start of the program (T2), and during 1 week after the last class of the program (T3).

Results showed that all of the main endpoints of the program significantly improved in the intervention condition (i.e., changes from T2 to T3), compared to the control condition (i.e., changes from T1 to T2). Moreover, children's adjustment at school and homeroom class increased in the intervention condition, compared to the control condition. However, implicit affect was unchanged.

This study suggests that the program is effective for enhancing self-confidence, along with adjustments at school and in class. Future research that examines the sustainability of the effectiveness of the program is planned.

The authors have not supplied their declaration of competing interest.