BACKGROUND: Promotion of oral health in children is recognized as one of the components of health-promoting schools (HPSs). However, few studies have addressed supportive school environments for children's oral health. This study aimed to evaluate the status of dental caries in school children at HPSs, with the objective of examining the impact of a supportive school environment for oral health, considering the lifestyles of individual children and the socioeconomic characteristics of their communities. METHODS: Data of 2043 5th-grade students in 21 elementary schools in Ichikawa city between 2008 and 2013 were analyzed. Children's oral health status was evaluated using the decayed, missing, and filled permanent teeth (DMFT) index. A self-reported lifestyle questionnaire, a survey of the school environment promoting tooth-brushing, and community socioeconomic characteristics derived from the National Census data were included in the analyses. Bivariate analyses were conducted to evaluate the children's DMFT status, and zero-inflated negative binominal (ZINB) regression was used to assess the relationships between DMFT and other variables. RESULTS: Prevalence of dental caries in the permanent teeth of 5th-grade children (aged 10-11 years) was 33.3%, with a mean DMFT score (± SD) of 0.83 ± 1.50. According to multilevel ZINB regression analysis, children from schools with after-lunch tooth-brushing time showed a higher odds ratio (OR) for excess zero DMFT (OR = 1.47, 95% CI = 1.00-2.15, P = 0.049) as compared to those from schools without it. Neither bivariate analysis nor ZINB model analysis revealed any significant influence of children's gender or use of a toothpaste with fluoride. CONCLUSIONS The school-based environment supportive of oral health was significantly associated with a zero DMFT status in children. School-based efforts considering the socioeconomic characteristics of the area warrant attention even with declining prevalence of dental caries.