The Exploratorium Teacher Institute (TI) is a teacher professional development center that offers comprehensive, multiyear professional learning institutes; classroom coaching and mentoring; and teaching tools to middle and high school science teachers. The TI staff is composed of a team of PhD scientists and veteran secondary science educators who work in concert to provide teachers with resources and experiences that develop the content knowledge and pedagogical skills necessary for teaching authentic science content through student-centered activities (McDermott and DeWater 2000). All of