Monitoring the quality of Mathematics education and taking actions to address its challenges is one of the many ways in attaining a countrys growth and development. The national mean percentage score (MPS) of Filipino learners in the National Achievement Test (NAT) for Grade 6 and Year IV along Mathematics subtest is still not yet at 75% passing rate. Thus, the study identified the proficiency level of the Grade 7 learners least mastered competencies along topics in Numbers and Number Sense with an end view of improving their proficiency levels. A one group pretest-posttest design type of research using a test instrument with a computed reliability coefficient of 0.83 was utilized. Moreover, the developed lessons on Number and Number Sense served as the intervention in improving the competencies of the respondents. Generally, there were significant increases on the proficiency level of the students after the implementation of the lessons, however, the fact that the learners were still low proficient on conceptual understanding and procedural skills along the identified competencies is undeniable. Hence, continuous monitoring of the learners focusing on the identified competencies maybe considered as part of the pre-evaluation of teachers to their grade 7 classes to integrate reinforcement in the improvement of the learners proficiency in the identified least mastered competencies.