This action research aimed to use worksheet and modules in Grade III Mathematics to increase the performance level of the pupils in understanding of numbers and addition of whole numbers. The researcher used worksheets for group activities, think-pair-share, pair-share and group games as well as the use of modules which is supplemented by some concrete instructional materials. This study was conducted during the third quarter of the school year 2013-2014 at Masisit Elementary School, Masisit, Sanchez Mira, Cagayan with 42 Grade III pupils as respondents.
Before the conduct of the study, pretest showed that the pupils had already minimal knowledge about the topics. They already had ideas about the concept to be taught because related topics were possibly taken in previous lessons or some questions given were related to their previous experiences. The pupils had correct responses but the mean percentage showed that the knowledge possessed by the pupils were not yet enough to understand totally the concept. Result showed that mastery or performance level of the pupils can be increased by supplementing concrete materials, giving group activities, showing group works in class, explaining processes, giving intensive examinations, homework and relating topics to pupils' everyday experiences.
Results reveal that the teaching materials used in this study were effective as shown by the increased mastery levels of pupils. The t-test result also showed that there is significant difference between the pretest and the posttest conducted and it is significant at <0.05 two tailed levels of significance.