Background: Oral diseases are common and widespread around the world. The most common oral diseases are preventable and early onset is reversible. Myanmar faces many challenges in rendering oral health services because about 70 percent of the total population resides in rural areas. These relate to the availability and accessibility of oral health services. Therefore, oral health education is one key element to prevent oral diseases and to promote oral health.Methods: A quasi-experimental study was carried out at Basic Education Middle Schools in rural areas of Magway Township to study the effectiveness of oral health education on knowledge and behavior of eight to ten-year-old school children. A total of 220 school children, 110 from the intervention school, and 110 from the control school participated in this study from 2015 to 2017. Data were collected before and after intervention in the two groups by using a self-administered questionnaire. Tooth brushing method data were collected by direct observation with a checklist. Oral health education was provided at eight weekly intervals for one year. At one and a half years, third-time data collection was done on the intervention group to assess retention. Chi-square test, two samples t-test, one way repeated measure ANOVA were used for data analysis. The study was approved by the Institutional Review Board at the University of Public Health,Yangon, Myanmar.Results: There were significant differences between the two groups in oral health knowledge (p<0.05) except one and also in behavior (p<0.001) after the intervention. A positive effect of the intervention was found in the intervention group. The intervention had a significant effect on the sustainability of the correct knowledge and behavior of the intervention group although the education session was stopped for six months (p<0.001). Their mean knowledge and behavioral scores at three different points got at these times were (2.45±1.12 and1.56±0.90) at baseline, (3.79±1.12 and 3.60±1.21) at one year after education, and (4.07±0.98 and 3.24±1.31) at six months after cessation of education, respectively. Conclusions: The repeated oral health education was effective to promote and sustain oral health knowledge and behavior.