This study examined the effectiveness of Project La‑Le‑Li, a literature‑centered and language‑integrated instructional intervention, in improving the reading comprehension proficiency of Grade 9 learners at St. Paul College, San Rafael, Inc. during School Year 2025–2026. Employing a quasi‑experimental design, the study compared the pretest, posttest, and retention test performances of control and experimental groups to determine both immediate and sustained effects of the intervention. Results indicated that the two groups were statistically equivalent at pretest. Following the intervention, the experimental group achieved significantly higher posttest scores than the control group, with a substantial proportion of learners reaching the “Proficient” level, while the control group demonstrated only marginal improvement. Retention test findings further revealed a significant increase in the experimental group’s scores compared to posttest results, indicating sustained and strengthened comprehension gains over time. Inferential analyses confirmed significant differences between the posttest performances of the two groups and between the experimental group’s posttest and retention scores. Qualitative insights from learners corroborated these findings, highlighting increased engagement, strategic reading behavior, and confidence resulting from the intervention. The results provide strong evidence that Project La‑Le‑Li is an effective and sustainable instructional model for enhancing reading comprehension and long‑term learning retention among secondary‑level learners.