This paper presents reflections on 12 years of school-wide professional development at a university-based preschool. The professional development focused on the Center for Research on Education, Diversity, and Excellence (CREDE) Standards, Vygotskian strategies that emphasize assisted performance, joint activity, and verbal interactions. Both formal and informal professional development were used. A study investigated whether educators' use of CREDE practices were sustained 12 years after initial professional development and the influences of the professional development on the school's institutional identity. The educators were observed interacting with children and interviewed about their practice. Documents from the preschool were also analyzed to determine the extent to which CREDE was integrated into its institutional identity. Results indicated that all of the teachers used the CREDE practices, although some of the newer teachers were not familiar with CREDE terminology. Informal professional development and administrators' support appeared to sustain the practices. The Center's institutional identity changed over time to incorporate CREDE and this coincided with the professional development and educators taking more ownership of the CREDE practices and how they could be applied in their settings.