The present study examined the extent to which adaptive feedback and just-in-time writing strategy instruction improved the quality of high school students' persuasive essays in the context of the Writing Pal (W-Pal). W-Pal is a technology-based writing tool that integrates automated writing evaluation into an intelligent tutoring system. Students wrote a pretest essay, engaged with W-Pal's adaptive instruction over the course of four training sessions, and then completed a posttest essay. For each training session, W-Pal differentiated strategy instruction for each student based on specific weaknesses in the initial training essays prior to providing the opportunity to revise. The results indicated that essay quality improved overall from pretest to posttest with respect to holistic quality, as well as several specific dimensions of essay quality, particularly for students with lower literacy skills. Moreover, students' scores on some of the training essays improved from the initial to revised version on the dimensions of essay quality that were targeted by instruction, whereas scores did not improve on the dimensions that were not targeted by instruction. Overall, the results suggest that W-Pal's adaptive strategy instruction can improve the quality of students' essays overall, as well as more specific dimensions of essay quality.