This study reports findings from a multisite cluster randomized controlled trial designed to validate and scale up an existing successful professional development program that uses a cognitive strategies approach to text-based analytical writing. The Pathway to Academic Success Project worked with partner districts affiliated with 4 National Writing Project (NWP) sites in southern California. Informed by a wide body of research on the efficacy of strategy instruction to enhance students' academic literacy, the intervention aimed to help secondary school students, particularly Latinos and mainstreamed English learners, to develop the academic writing skills called for in the rigorous Common Core State Standards for English Language Arts. Two hundred thirty teachers from partner districts affiliated with the NWP sites were stratified by school and grade and then randomly assigned to the treatment or control group. Treatment teachers participated in 46 hrs of training and learned how to apply cognitive strategies by using an on-demand writing assessment to help students understand, interpret, and write analytical essays about nonfiction texts. Multilevel models revealed significant effects on a holistic measure of an on-demand writing assessment (d = 0.32) as well as on 4 analytic attributes: content (d = 0.31), structure (d = 0.29), fluency (d = 0.27), and conventions (d = 0.32). Four dimensions of scaling up--spread, reform ownership, depth, and sustainability--are also discussed.