This study determined the least learned competencies in the Rapid Mathematics Assessment (RMA) among Grade 5 learners of Sanyata Elementary School, Bislig City Division, as basis for developing an enhanced school-based Mathematics Intervention Program. It used a quantitative non-experimental descriptive design and records-based analysis of official beginning-of-school-year (BOSY) and end-of-school-year (EOSY) RMA results. Complete enumeration was applied to the available Grade 5 class records: 20 learners had BOSY records and 23 learners had EOSY records. The official Grade 5 RMA and a researcher-made Competency Analysis Matrix were used to organize scores by learning area and competency. Data were analyzed using frequency count, percentage, mean percentage score (MPS), and ranking. Overall performance increased from 32.97% MPS at BOSY to 69.97% at EOSY. Number and Algebra reached 75.36% MPS, Data and Probability reached 71.74%, and Measurement and Geometry remained the weakest domain at 64.35%. Sixteen competencies remained below the 75% mastery criterion. The lowest-performing competency was measuring and drawing angles using a protractor (30.43%), followed by converting units of measure (34.78%) and adding dissimilar fractions or mixed numbers (34.78%). The findings show that RMA records can provide a practical basis for a targeted, school-based intervention emphasizing hands-on geometry activities, guided practice in number operations and fractions, graph interpretation, diagnostic grouping, and regular progress monitoring.