Rambo-Hernandez and McCoach's analysis into the longitudinal growth of high-achieving students offered two conclusions about the reading growth of high achieving students: high-achieving students lose less ground in reading during the summer, but they exhibit less growth over the school year. This study will seek to replicate the reading results of the Rambo-Hernandez and McCoach's study and include an analysis of mathematics growth with initially high-achieving, third grade students in both the school and summer months. Through a three-level hierarchical linear model covering 1541 third graders, this study analyzes the differences between the school year and summer growth rates of the high-achieving students against other students that scored above the mean on MAP assessments. Students identified as being in the top 10% nationally at the start of the third grade grew less over the course of the school year compared to their peers in both mathematics and reading but showed signs of accelerated growth at the end of the study. [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.]