Block scheduling has been touted as a reform effort for American schools (Trump, 1959; Zepeda & Mayers, 2006). Block scheduling allows teachers to use the additional class time to vary the activities in the classroom and move away from the lecture model and affords teachers the opportunity to utilize more student-centered activities to engage the students. The study examines the instructional strategies used in two high schools in Southeastern Pennsylvania: one on a block schedule and the other on a traditional schedule. This mixed-methods, multi-case study utilized an online survey and semi-structured interviews in order to ascertain to what extent teachers on a block schedule use different instructional strategies than teachers on a traditional schedule. Additionally, the study sought to understand what factors influence teachers' choice of instructional strategies in the classroom. Sixty-eight teachers participated in an online survey about their teaching practices. Using a t-test and ANOVA, it was determined that teachers in this study who teach using a block schedule utilize not only more strategies and activities than their counterparts who utilize a traditional schedule, but they also utilize more student-centered strategies and activities. No difference was found in the use of teacher-centered strategies between the groups. Eight teachers and four administrators subsequently participated in semi-structured interviews that probed at the factors that influence which strategies teachers utilize. The research found that teachers perceive professional learning communities, both formal and informal, as more important than the in-service model of professional development teachers receive. Teachers also perceive time as a factor that either promotes or impedes their use of student-centered strategies in the classroom. Finally, the teachers indicated that state, district and building expectations do impact their choices of instructional strategies. [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.]