Bullying has far-reaching consequences, and effective bullying prevention can have a long-lasting impact on the well-being of many individuals. To confront bullying in schools, the Olweus Bullying Prevention Program (OBPP) has been implemented in Lithuanian schools since 2008. The OBPP has already been implemented in 466 schools and about one-third of these schools continue to participate in the Olweus Quality Assurance System (OQAS). It has already been more than 10 years since the 1st cohort of schools started to implement the OBPP. This cohort consists mainly of schools from the three largest cities in Lithuania: Vilnius, Kaunas, and Klaipeda. Eight schools of this cohort are still participating in the program. We decided to analyze changes in the rates of bullied students in these schools to see what they had achieved from 2008 to 2019. Every November, students in grades 3rd to 10th complete Olweus Bullying Questionnaire's (OBQ) Lithuanian version. We analyzed three time points: start of the implementation of the program in 2008, end of the initial implementation stage and start of the OQAS in 2010, and survey results in 2019. There were 3723 students participating in the survey in 2008, 3663 in 2010, and 3736 in 2019. For the analysis, we used the dichotomized being bullied variable: "How often have you been bullied during the past couple of months?." We used a common cut-off of at least 2 or 3 times a month or more to define someone who was being bullied. Results were analyzed by using multilevel logistic regression using a logit link. There was a significant reduction (p < 0.05) at the initial stage of the program among 5th-10th grade girls and 5th-8th grade boys. As far as OQAS is concerned, there was a significant reduction in bullying rates among 3rd-8th grade students. During the period of 11 years, 1st cohort OBPP schools significantly reduced bullying rates among 3rd-10th grade girls and 3rd-8th grade boys.