This study examined the performance gap experienced by high achieving grade four and five students at the Kallang International Day School (KIDS) who were not demonstrating growth in math results from fall to spring as measured by the Measures of Academic Progress (MAP) test (NWEA, 2017). The purpose of this study was to apply the gap analysis problem- solving framework (Clark & Estes, 2008) to identify root causes of the knowledge, motivation and organizational factors that prevented teachers from effectively teaching 100% of the math content required for greater numbers of high performing students to demonstrate growth in the MAP test. The subjects of this study were teachers of grade four and five at the Kallang International Day School. Interview and observational data were collected and analyzed and used to validate and inform possible solutions for the knowledge, motivation and organization influences. Research-based solutions were recommended to close the knowledge, motivation and organization gaps, and included providing teachers with frequent, accurate, specific and timely feedback regarding their use of differentiated mathematics instruction for student groupings and using learning community time to collaboratively plan specific conceptual and skills based math lessons differentiated for high performing students. Critical behaviors of the stakeholders were also examined and recommendations included generating student math goals based on fall MAP results, teaching with the Effective Mathematical Teaching Practices, (NCTM, 2014) and using them to create plans for modifying classroom instruction to enhance high performing students' progress. The outcomes of this study may be used by this school and others to improve the growth in math achievement for high performing students. [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.]