The goal of greater student engagement has led districts to turn to technology, specifically, one-to-one (1:1) or a device for every student. This qualitative case study explored teachers' mobile device use to implement high-leverage instructional practices that engage students, advance equity, and improve student learning outcomes for underserved students in one high school and its feeder middle school in the southernmost part of California. The research methods included four different sources a Qualtrics Online survey titled, Teaching with a 1:1 Mobile Device, Semi-Structured Interview questions with 28 core content teachers and two principals, 30 classroom observations, and the review of some of the study district's public documents such as the Educational Technology Plan, School Plan for Student Achievement (SPSA) and Local Control Accountability Plan (LCAP). This study examined the teachers' current instructional practices with a 1:1 mobile device and their impact on student engagement, advancing equity, and improving student learning outcomes for underserved students. The study aimed to inform policymakers, school boards, administrators, and teachers of the best-instructional practice options to implement a 1:1 device technology initiative to provide authentic world learning experiences for underserved students. Five central categories and subsequent sub-categories emerged from the researcher's inductive and appreciative data analysis approach: (1) High-leverage instructional strategies; (2) Engagement; (3) Advancing Equity, (4) Improving Student Outcomes; and (5) Leadership. These themes led to subsequent themes that provided a deeper understanding of the study participants' perspectives, experiences, and current status of Exploring Teachers' High Leverage Instructional Practices with a 1:1 Mobile Device. [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.]