With an increase of English language learners in public schools across the United States, the importance of addressing the needs of students who require language access in their home language has resulted in an increase in the implementation of dual language programs. This increase continues to challenge educators to provide effective programs that provide quality instruction for English language learners. This has prompted schools to offer a two-way dual language program as an educational bilingual option to assist in meeting the needs of emergent bilingual students. In this qualitative case study, the researcher explored the extent to which school principals' leadership and decision-making processes exert influence on the operations of two-way dual language classrooms including English language learners/multilingual learners at the elementary school level. The researcher also focused on the guiding principles of program design and implementation for dual language programs, which are organized into seven strands: program structure, curriculum, instruction, assessment and accountability, staff quality and professional development, family and community, and support and resources. This research was based on a qualitative case study methodology. Data were collected through interviews with administrators, focus groups with dual language teachers, survey responses, and artifacts. The theoretical framework of self-efficacy and the decision-making process guided the analysis. The study findings provide guidance and information for principals so that they may recognize key elements and strategies that will guide them in fostering and operating effective two-way dual language programs among their staff. [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.]