Digital technologies are prevalent in society and K-12 classrooms today and the belief that educational technology can be a transformative agent of change in education is ever increasing. However, the use of technology as a transformative learning tool for all students has not yet been realized. Research in this area indicates that teachers are the leading factor impacting the utilization of technology for learning. Focused professional development along with time to develop curriculum and lessons has been identified as critical factors in changing the way teachers and students utilize technology. The purpose of this explanatory single case study, with multiple units of analysis, was to examine the experiences and practices of nine teachers in a technology-rich high school setting to better understand the impact of a TPACK based professional development model, to understand how and why teachers make decisions regarding instructional technology integration, and to determine how their technology integration met the TPACK model of instruction. Findings from the study revealed that the professional development model based on TPACK framework and effective professional development strategies increased teachers’ use of technology, how they considered using technology and changed their instructional focus from teacher to student-centered practices. Additionally, teachers’ considerations for instructional technology during planning were influenced by their teacher-centered or student-centered ideas. Finally, teachers who successfully implemented technology based on the Technology Integration Observation Instrument were those who were well versed in active learning strategies, learner-centered in their planning and implementation of instructional strategies, have the greatest number of years experience and exposure to the TPACK training model, while having varying levels of technology efficacy. The study provided evidence to support the idea that transformational educational change through technology has little to do with the technology itself; instead, it is dependent on the pedagogical knowledge of the teacher and the context of the professional development provided to teachers. It is increasingly evident that the change sought in teaching and learning will only come about by a change in the pedagogical practice of teachers who are appropriately prepared with student-centered learning activities and content knowledge that utilizes technology as an instructional tool in order to facilitate and impact learning.