The purpose of this study is to explore the relationship between the personality traits, learning environment and academic achievement of children in mixed-grade versus traditional classrooms. The conflicting existing research on the efficacy of mixed-grade classrooms suggests there may be characteristic differences between children that impact success in these classrooms. Understanding whether and to what degree a relationship exists would help to ensure students are sorted into classrooms that optimize their learning capacity and promote academic success. This is the first known study to date that explores the associations between and predictability of children's personality traits using the NEO-PI-3 as an informant rating system, level of academic achievement, type of classroom, and parent perception of their child's learning climate. The current study explored these relationships by surveying parents of elementary school children in traditional, mixed-grade, and a combination of traditional and mixed-grade classrooms. Participants were asked to complete an adapted version of the NEO-PI-3 based on their perception of their child's personality and personality traits, and the Learning Climate Survey as an objective measure of their perception of their child's learning environment. Results from the present study indicate there is no significant association between type of classroom, children's parent-rated personality traits, and parents' perceptions of their child's learning climate. This conclusion is consistent with previous literature, that there are no significant differences between classroom designs even when personality is accounted for. It is reassuring for parents and educators to know that neither classroom design has yielded significant outcomes for students at this age. Families and schools can continue to make decisions that fit their preferences or maximize their resources. However, both parties would benefit from future studies or larger samples that assess the children directly, involve the input from teachers and potentially follow the children longitudinally to assess long-term consequences of classroom design. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]