In 1988 Saint Mary's College received a grant from Lilly Endowment, Inc. to create a program to improve the quality of science education in the local public and private schools. As part of applying that grant we created one-week summer work-shops for elementary and middle school teachers (K-8) based on guided inquiry methods of education. Each summer from 1999 to 2002 we have taught sixteen teachers in two week-long Teacher Science Institutes (TSI). This paper describes one part of the content and processes used in our workshops. Primarily it describes the teachers' enthusiastic shift to a constructivist, student-centered, guided inquiry pedagogy for science in their classrooms.