As part of our professional development intervention, this study examined third-grade ELL students' writing achievement that included “form” (i.e., conventions, organization, and style/voice) and “content” (i.e., specific knowledge and understanding of science) in expository science writing. The study included six treatment schools from a large urban school district. Data were collected from three different groups of students over 3 separate years. Students displayed a statistically significant increase each year, and the gains were incrementally larger over the 3-year period. Students at ESOL levels 1 to 4 made gains comparable to those who had exited from ESOL or never been in ESOL.