This study assessed the competency level of TVL–CSS Senior High School students at Concepcion F. Llorin National High School, Sagurong, Pili, Camarines Sur, and developed a supplementary mobile learning application to address identified learning gaps. Specifically, it evaluated students’ competencies in installing and configuring computer systems, setting up computer networks and servers, and maintaining and repairing computer systems and networks. Using a descriptive research design, the study involved forty (40) students and ten (10) expert validators, including education supervisors, master teachers, ICT teachers, and IT experts. Data were analyzed using weighted mean. The findings revealed that students demonstrated low competency across all areas, with an overall pre-test mastery level of 23.28% (Unmastered), indicating insufficient foundational knowledge and technical skills. In response, an offline mobile learning application, L.A.R.A (Learning Assistance and Reinforcement App), was developed to provide interactive, self-paced, and curriculum-aligned learning materials. The application was validated as highly acceptable, obtaining ratings of very satisfactory in content (3.99) and Excellent in technical functionality (4.33), and very satisfactory in instructional quality (3.70), usability and engagement (4.18), and overall acceptability (4.10), although improvements in motivation and critical thinking components were recommended. Post-test results showed an increase in mastery to 37.55% (Slightly Mastered), indicating measurable improvement in all competencies. The study concludes that the mobile learning application is an effective supplementary tool that enhances students’ competencies, though sustained use and instructional reinforcement are necessary to achieve full mastery. It is recommended that schools strengthen competency-based instruction, increase hands-on activities, and continuously refine mobile learning resources.