Active Learning in Maths and Science (ALMS) was a six-month face-to-face professional development program for middle school maths and science teachers carried out between June and November, 2010 in two Indian states. ALMS's theory of action is grounded in the belief that collaborative learning serves as a "gateway" to learner-centered instruction. Designers theorized that this shift from individual to collaborative learning would redefine the teacher's role; alter the teacher and student relationship; change teachers' organizational, instructional and assessment practices; and begin to lay the groundwork for an eventual shift toward full learner-centered instruction. As this paper will discuss, this proposed theory of action was largely confirmed. Over 80 percent of teachers across the two states regularly implemented collaborative learning techniques and began the larger journey toward learner-centered instruction. This implementation also resulted in a number of benefits for students, including greater levels of engagement, increased confidence, and improved behavior. The research also suggests that when teachers see positive changes as a result of their actions, their deeply-held beliefs about traditional instruction may conflict with what they in fact witnessed in their classrooms. This is the beginning of the evolution of change.