Though the No Child Left Behind Act of 2001 requires secondary students with Asperger's syndrome (AS) to take high-stakes mathematical tests, many students with AS exhibit weaknesses in mathematical and executive functioning skills. The purpose of this mixed-methods case study was to explore the use of differentiated mathematical strategies with secondary students with AS. The study was grounded in the theories of zone of proximal development, information processing, structural cognitive modifiability, and metacognition. Research questions examined (a) the relationship between AS students' executive functioning skills and their performance on high-stakes math tests, (b) the observable associations between the executive functioning skills of students with AS and the differentiated mathematical strategies used to teach them, and (c) the differentiated mathematical strategies students with AS perceive as the most effective for learning math. Quantitative data included 6 students' test scores and questionnaires; qualitative data included field notes from 46 observations. Based on correlational analysis, thematic coding, and descriptive analysis, no statistically significant correlations were found between math, processing speed, or word memory; however, there was a statistically significant difference between the AS students' processing speed and word memory, with higher scores for processing speed. Observable associations were found between AS students' executive functioning skills and strategies used to teach them. Differentiated strategies were rated by AS students. The results indicated 3 differentiated strategies were ranked as very helpful when learning math skills. By providing recommendations on the mathematics teaching strategies best suited for students with AS, positive social change may occur by improving student outcomes. [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.]