The Rice Engineering Design Experience (REDE) is developing and implementing a comprehensive professional development program for in-service high school teachers to prepare them to teach engineering design and problem solving, and to use design-based teaching approaches in their science curriculum. The program uses a constructionist, immersion pedagogy as part of an unconventional three- phase learning cycle. Pre- and post-test results for the first summer workshop indicate significant gains in understanding the engineering design process among the teachers. The second year of the program will focus on developing and implementing design-based curriculum modules covering science concepts. The presentation will describe a similar evaluation of the 2010 workshop, and the changes in first-year classroom practice using observations by outside evaluators. Best practices, lessons learned, and remaining challenges will be discussed.