The Literacy Design Collaborative (LDC) was created in 2009 to support schools' implementation of rigorous college and career ready standards for English language arts (ELA). Combining evidence-based principles of professional development with a systematic design process, LDC helps teachers to embed literacy skill development throughout their content area curricula and promotes teachers' engagement in formative assessment and continuous improvement practices. UCLA's National Center for Research on Evaluation, Standards, and Student Testing (CRESST) has served as LDC's independent evaluator since 2011 and is currently completing a 5-year, nationally funded study of LDC's implementation and impact. This policy brief summarizes study results from a large, urban district on the West Coast. The brief starts with background on LDC and study methodology and then shares study findings, which demonstrate LDC's substantial effects on student learning. [For related reports, see "Literacy Design Collaborative 2017-2018 Evaluation Report. CRESST Report 863" (ED600053) and "Literacy Design Collaborative 2017-2018 Evaluation Report. CRESST Report 867. Revised" (ED606343).]