Teaching of grammar plays a vital role in language teaching. One cannot communicate effectively when grammar is poor and weak. This study aimed at examining the effectiveness of Strategic Intervention Material (SIM) as an instructional tool in improving the English grammar skills of the Grade 10 students in one of the schools in the Division of Bukidnon during the academic year 2019-2020. The quasi-experimental design was used to determine whether or not there was a difference between the pretest and posttest scores of the students after Strategic Intervention Material (SIM) was integrated in teaching grammar. Purposive sampling was utilized with pre-selected heterogeneous classes with 78 respondents, 39 respondents for each of the control and experimental groups. A researcher-made instrument was distributed to the respondents comprising of 50 multiple choice-based questions. Frequency distribution, standard deviation, t-test, double difference and ANOVA were the statistical tools used to treat the data. The overall pretest result revealed intermediate level for both the control and experimental groups. Overall posttest result for the control group remained as intermediate level, while the experimental group improved to advanced level. Hence, the result disclosed that there was a significant difference between the pretest and post-test scores of the experimental group after Strategic Intervention Material (SIM) was integrated in teaching grammar. The study also depicted no significant difference in students’ demographic profile such as age, sex and academic performance and level of English general grammar skills. Therefore, findings of this study indicate that Strategic Intervention Material (SIM) plays an important role in the present and future education of this generation and that there are other variables to consider for explaining significant differences in the level of their grammar skills.