The study determined the teachers’ dominant approaches used in teaching English as a second language and their influence on the grammatical skills of the high school students. The respondents of the study were the randomly sampled 2nd year and 3rd year high school students and English teachers of Liceo de Cagayan University. The study used the descriptive design using a researcher-made questionnaire that elicited data on the teachers’ approach in teaching the selected grammar lessons and the students’ level of grammar skills. As found out, the dominant approach in teaching English grammar was communicative. The students did poorly in subject-verb agreement and noun-adjective agreement, and well in verb tenses. Overall, the students did fairly in English grammar.