Early failure to learn writing skills might go unnoticed and unremedied unless teachers adopt specific strategies for identifying and supporting students who learn at a slower pace. We implemented a Response to Intervention (RTI) program for teaching narrative writing. Over 18 months from start of primary school, 161 Spanish children received instruction in strategies for planning text and training in handwriting and spelling, and completed very regular narrative writing tasks. Data from these tasks were analysed to identify students at risk of falling behind. These students then completed additional, parent-supervised training tasks. During this training the quality of these students' texts improved more rapidly than those of their peers. The resulting decrease in difference relative to peers, as measured by both regular narrative tasks and by post and follow-up measures, was sustained after additional training ceased. Interviews and questionnaires found good parent and teacher buy-in, with some caveats. Findings therefore indicate the feasibility and potential value of a RTI approach to teaching writing in single-teacher, full-range, first-grade classes.