Some colleges of education and urban school districts have established collaborative Professional Development Schools (PDSs) to prepare teachers across the learning-to-teach continuum (pre-service to in-service to instructional leaders) to address the particular needs of low-income, culturally and linguistically diverse (LI/CLD) students. Outcomes, either in regard to K-12 pupils or to pre-service and in-service teachers, have been infrequently examined despite the proliferation of these reforms. Urban PDS experiments encounter many challenges that obstruct efforts to create learning environments that embody the "engaged pedagogy" necessary for LI/CLD students to succeed. This article examines the findings from preliminary assessments developed for a large-scale PDS experiment undertaken by a California state university and its partner urban schools. Despite the limitations, these have provided important information that has sustained the innovative work unfolding in the PDSs. In addition to reviewing the approaches to assessment undertaken by this PDS project, this article considers the links between assessment and program development and innovation. (Contains 2 tables and 2 notes.)