This study examined the classroom management and/or training that influenced the implementation of flexible grouping in upper elementary classrooms. The goal of the study was to identify classroom management strategies that would enable upper elementary teachers to effectively implement flexible grouping as a method of differentiated instruction. The qualitative approach was utilized to meet the goals of the study. The participants of this study were selected from a population of grades 3-5 teachers who were members of teacher related Facebook groups. Purposive sampling was used to gather a sample of 15 grade 3-5 teachers who actively employ flexible grouping in the classroom. Data was gathered using semi structured interviews. Axial coding was used to analyze the data. The study found that classroom arrangement, teacher proximity, desk arrangement and noise levels are factors that impact the implementation of flexible grouping and that teachers lacked classroom management training. It is recommended that future research studies collect data from a larger sample and the data be analyzed by several researchers. It is also suggested that future studies assess the impact of teacher training on the success of flexible grouping. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]