This quantitative descriptive-correlational study was conducted to investigate the effectiveness of senior high school teachers and the academic performance of their students in selected schools in New Bataan, Davao de Oro, for the school year 2020-2021. New Bataan National High School, Camanlangan National High School, and Andap National High School. Results revealed that the teachers’ competencies in the knowledge of the subject matter, assessment strategies, teaching strategies, classroom management, and attitude and behavior were all evaluated high with descriptive equivalents of often manifested. Further, the result of the student’s academic performance as measured by their academic grades was satisfactory. The results also revealed no significant relationship between the competencies of the senior high school teachers and the students’ academic performance. From the results of the study, it was recommended that the teacher must use varied assessment strategies to cater to the needs of intellectually diverse students. Teachers must always use a variety of methods and strategies to answer the diverse needs of the students and to motivate them to be more active in classroom interaction; and further research is encouraged to examine the relationship between teachers’ competencies and the academic performance of the students by increasing the number of respondents and additional variables in teachers’ competencies closely.