Joellen Killion reports on the results of a five-year professional development intervention consisting of workshops and curriculum units conducted in six elementary schools in an urban district to gauge teacher knowledge and practices in science instruction for English language learners. The study looked at predictors of teacher change that included grade level taught, experience teaching, and courses in science. The intervention responded to changing student demographics, teachers' insufficient preparation to meet the needs of English language learners in urban schools, and heightened demands for accountability. Researchers measured change in teacher knowledge and practice using two instruments: 1) a questionnaire given at the inception of the study to serve as a baseline and then each year of participation and 2) collected data through a fall and spring classroom observation using an observation guide aligned with four domains. The analyses of the questionnaire indicated that significant change between initiation of the intervention and the end of year one occurs in scientific understanding, scientific inquiry, and English language development. Across all years of the intervention, teacher practice in scientific knowledge and English language development improved, although not significantly. The study demonstrated that change in teacher knowledge and practice can be observed and measured using appropriate instrumentation, although an important limitation of the study was the lack of baseline observation data collected prior to the inception of the intervention.