We evaluate how higher- vs. lower-scoring middle-school students differ in their composition processes when writing persuasive essays from source materials. We examined differences on four individual process features--time taken before beginning to write, typing speed, total time spent, and number of words started. Next, we examined differences for four aggregated process measures: fluency, local editing, macro editing, and interstitial pausing (suspending text entry at locations associated with planning). Results showed that higher vs. lower scoring students were most consistently differentiated by total time, number of words started, and fluency. These differences persisted across two persuasive subgenres and two proficiency criteria, essay score and English language arts total-test score. The study's findings give a more complete picture of how the processes employed by more- and less-successful students differ, which contributes to cognitive writing theory and may have eventual implications for education policy and instructional practice.