This study explores the impact of the clustering technique in enhancing students’ writing performance in composing hortatory exposition texts. Conducted as Classroom Action Research (CAR) over two cycles, the research involved 15 twelfth-grade students at SMA Muhammadiyah 1 Rambipuji during the 2024-2025 academic year. Quantitative data were obtained from the writing rubric and analyzed using descriptive statistics to measure improvement across writing aspects. Qualitative data were collected through an observation checklist and analyzed using content analysis to examine students’ engagement, behavior, and learning motivation. In the first cycle, students exhibited limited engagement, weak organization of ideas, and low confidence. After pedagogical refinements in the second cycle – such as guided modeling, collaborative tasks, and scaffolding of structure – students showed marked improvement in motivation and writing quality. Their text reflected better organization, more persuasive content, and improved grammatical accuracy and lexical variety. The clustering technique helped the student visualize engagement. The findings suggest that clustering is an effective and practical pre-writing strategy for improving argumentative writing skills in EFL contexts.