Bullying behavior has reached pandemic proportions and is a growing concern in primary school. Most intervention programs in primary school are focused on bullying prevention or principally on the behavior of the bully. The purpose of this study was to explore whether a school-based bullying intervention program is an effective method for reducing bullying behaviors within the primary school population. The theoretical framework of effectiveness of a school-based bullying intervention program in this study was connected to the constructivist theory of learning proposed by Jean Piaget. Constructivists believe that a school-based bullying intervention program will facilitate moral reasoning and mediation choices underlying the arena of cognitive development. This study used a qualitative design, grounded theory approach introduced by Glaser and Strauss in 1967. Grounded theory is a systematic qualitative approach that was used to generate a theory that explained at a broad conceptual level from the participant's point of view. This study used semi-structured interviews to collect data and analyze it using grounded theory methods. The findings of this study were based on ten teachers' and ten administrators' insight on the effectiveness of a school-based bullying intervention program. Although there is conformity that school-based bullying intervention programs reduced bullying, and the respondents in this study revealed that some intervention programs showed impressive results, the overall general results of a school-based bullying intervention program from this study have been mixed and its effectiveness in primary school is still unclear. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]