Utilization of Sentence Diagramming Worktext: Enhancing Grade 11 Students Grammar Skills

English language proficiency is fundamental for academic success and global communication, yet many students struggle with grammar skills. This study investigated the effectiveness of sentence diagramming worktext in improving the grammar skills of Grade 11 students at Rajah Muda National High School in Tacurong City, Philippines, where English teachers consistently observed significant challenges in teaching grammar effectively. The research addressed the lack of literature on the use of sentence diagramming in the Philippine context, particularly in addressing the specific grammar challenges faced by Senior High School learners. A true experimental design with a descriptive-evaluative approach was employed, involving a control group receiving conventional instruction and an experimental group utilizing the sentence diagramming worktext. The sentence diagramming worktext was developed and validated by English language experts, ensuring its high quality and alignment with learning objectives. Data were collected through pre-tests and post-tests to measure students' grammar skills before and after the intervention. The findings revealed that the experimental group, who used the sentence diagramming worktext, showed a significantly greater improvement in their grammar skills compared to the control group. This suggested that sentence diagramming, as a visual and interactive learning strategy, can be a valuable tool for improving grammar skills, particularly in the context of writing composition. The study concluded that the sentence diagramming worktext was effective in enhancing grammar skills and recommended its adoption and implementation in Senior High School classrooms across the Philippines. The study also emphasized the importance of pre-assessment in identifying individual learning needs and personalizing instruction accordingly.