The purpose of this case study was to discover and describe the components of a "double-dose" math intervention that resulted in increased mathematics achievement for high school Algebra I intervention participants in an effort to inform local decisions regarding program improvements and to provide insight to other educators investigating mathematics interventions. Students participating in this "double-dose" intervention were assigned to two math classes. The first math class was a regular math class comprised of heterogeneously ability grouped students. Students from the first class who needed extra support populated the second daily math class. This homogeneous group of students was involved in learning experiences in which concepts were pre-taught and re-taught while addressing identified foundational gaps in math skills and developing perseverance and problem-solving skills. The data for this study were collected via student and parent surveys, instructor and administrator interviews, observations and analysis of documents. These qualitative data were supplemented by quantitative data of treatment and comparison groups acquired from state and local assessments in an effort to provide a more complete description of the intervention. This study was informed by Vygotsky's Sociocultural Theory and zone of proximal development. The results of the study indicated that the intervention had a statistically significant impact on student achievement while the qualitative data indicated improved affective qualities such as confidence and attitude toward mathematics. In addition, triangulation of all data sources showed five critical elements for the design and implementation of similar interventions: extending and focusing the learning time, using varied instructional strategies, basing instruction on student need, building relationships and refining the selection of intervention participants. [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.]