Current literature on dual language programs is focused at the elementary school level, while research at the secondary level remains sparse. Hence, this study addresses the literature gap by considering the impact of school organization and instruction on these programs. Specifically, this collective case study examines the effective features of secondary dual language programs by comparing programs at a charter middle school to a district middle school and a charter high to a district high school's dual language program. The researcher utilized the seven strands from the "Guiding Principles for Dual Language Education" to conduct this study, as these principles are regarded by educators to be an accurate means of assessing the success of dual language programs. Study design incorporated a mixed method approach where quantitative and qualitative data were collected and analyzed. The qualitative data consisted of surveys, interviews, and teacher observations, while data collected on students comprised the quantitative data. Triangulation occurred within the four schools to identify trends and comparisons. Teacher observations of the dual language programs revealed that the curriculum is aligned to standards, and instruction remains rigorous in both English and Spanish. The charter schools outperformed the district schools, as measured by Grade Point Average and Advanced Placement Spanish Language passing rates. Interviews indicated that staff quality and professional development remain the biggest challenge. Examination of student demographics found Initial Fluent and Reclassified English Learners generally performed as well as or better than English Only 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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]