The capacity to produce clear and correct sentences is essential for effective academic writing, particularly for senior high school students preparing for advanced studies. Among various grammatical structures, relative clauses play a vital role in improving sentence complexity, deepening ideas, and ensuring textual cohesion. Despite their importance, relative clauses remain a challenging aspect of English syntax for second language (L2) learners. Filipino learners, in particular, often demonstrate errors in relative pronoun selection and clause construction, often limiting their use of relative clauses to simple descriptive functions rather than leveraging them for richer discourse purposes (Salazar, 2020; Chen, 2016).