This mixed methods study examines the design process and capacity of four high school master schedules to provide language support while moving newcomer students successfully towards graduation and college prep coursework. All four schools house newcomer programs and reside in the same large urban school district. Through qualitative interviews, the study identified the political, economic, leadership, and organizational context in which master schedule design decisions were made and provided insight into the conditions necessary to create master schedules that prioritize the needs of English Learners (ELs) and newcomers. Specifically, the researcher documented the process of the master schedule creation, articulated goals and underlying principles guiding the design process, and the constraints or equity supports that impacted the final schedules. By analyzing high school newcomer transcripts for a cohort of students from 2015-19, the researcher examined how each school's theory of action for newcomers was operationalized and determined the degree to which it supported students to access language development support, persist, graduate, and complete A to G college prep coursework. Where master schedules were differentiated for students with interrupted formal education (SIFE), these modifications were also examined. The research found that having more expertise in the master scheduling process and widening the process to include more stakeholders resulted in stronger master schedules that aligned with best practices of sheltering students when needed and transitioning them over time to mainstream classes. These schools were also characterized by higher rates of graduation and college readiness. Quantitative findings revealed that while demographic characteristics such as being male, SIFE, and overage were associated with lower rates of graduation, A to G completion and persistence, some design features of master schedules had stronger associations with academic success. The strongest associations in master scheduling and graduation rates, A to G completion, and persistence related to participation in summer school and dual enrollment programming. Study results also demonstrated that where there was a strong college going vision for all students, newcomers graduated at higher rates, had higher rates of college readiness, and saw more equitable outcomes for SIFE, unaccompanied minors, and overage 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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]