This article problematizes evidence-based policies in the USA, using Dewey's (1916) education theory and findings from a school development project in 71 culturally diverse Arizona schools. The study asked three questions: (1) How do formal and informal school leaders work in teams to mediate between evidence-based policy requirements at federal, state, and district levels and the needs of culturally diverse students? (2) What leadership team practices contribute to school development as measured by improved student outcomes in school letter grades? (3) What values from evidence-based policies and democratic education are evident in effective school development? Evaluation methods featured qualitative interviews with leadership team members in 71 schools as well as a descriptive analysis of school letter grades based primarily upon student outcomes. Results indicated improved student outcomes in letter grades and enhanced leadership capacity and democratic values as well as evidence-based values that contributed to school development. The article concludes with next steps to expand the project to another region of the USA and a call for a balanced use of evidence (including standardized test scores) constructed through Dewey's notion of democratic values of education.