The "Framework for K-12 Science Education" and the Next Generation Science Standards have called on teachers to shift from having students "learn about" science topics to having students engage in a process of "figuring out" how and why natural phenomena occur. These reform documents push teachers away from a transmission-style (TS) approach to science teaching, in which students' ideas and ways of knowing are often ignored or treated as misconceptions. Instead, these reform documents require that teachers use a responsive instructional (RI) approach, in which student ideas are attended to and used as resources for learning. Research on the use of RI provides evidence of greater student learning gains compared to those observed with use of TS. Though RI has been called for within reform efforts and its benefits have been demonstrated, this approach is not common in most science classrooms and it can be challenging for teachers to learn to plan for and enact this type of instruction. Most studies of RI focus on teachers' enactment, often focusing on how a teacher "elicits," "interprets" and/or "responds" to student ideas during instruction. However, the way a teacher plans for instruction strongly influences enactment, as teachers do not commonly stray from their lesson plan once instruction has begun. Therefore, if a teacher is to enact RI, they must first plan ways to attend to and use student ideas as resources for learning or engage in what I call responsive planning. One tool that may support a teacher's "responsive planning" is a learning progression (LP). As a model of how student ideas may change over time, an LP used during planning may help (1) to increase teacher awareness of commonly held student ideas to plan for and (2) in making decisions about instructional next steps that build on student ideas. Therefore, this case study investigated how a high school physics teacher with a TS approach to science instruction began to intentionally engage, with PD support, in responsive planning; how his planning changed over time; and how his planning was supported with the use of an LP. Data was collected during PD-supported planning meetings held during a 6-week force and motion unit that was taught twice, once in the Fall, and again, in the Spring. At the start of the study, the participating teacher's planning was informed by his TS instructional approach. However, over time, the teacher made changes across three dimensions of responsiveness: (1) the amount of "attention" he planned to give to student ideas during instruction, (2) the type of "discourse" structures he planned to use and (3) the types of "roles" he planned to have students take on during instruction. As compared to his original TS-informed lesson plans, the teacher's Fall eliciting lesson plans showed increased attention and role responsiveness. The attention responsiveness of his Fall responding lessons also increased from the beginning to end of the unit. As compared to the Fall responding lessons, the teacher's Spring responding lessons showed more discourse and role responsiveness. Over time, these gradual shifts in attention, discourse and role amounted to significant changes in the responsiveness of his lesson plans. Data also suggests that these shifts occurred when PD support focused on shifting one dimension at a time, rather than multiple at once. Additionally, the teacher used the LP both when his planning followed a TS approach and as it transitioned to being more responsive. Together, these findings suggest: (1) that PD providers could use a similar approach to supporting teachers as they shift toward responsive planning (starting with one dimension, rather than trying to shift multiple dimensions at once) and (2) an LP may be useful, when coupled with PD, to teachers as they shift toward more responsive planning. [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.]