Abstract. Insufficiencies in effective learning materials, poor English comprehension, and abrupt shift to alternative learning modalities are a few of the many possible root causes of low proficiency levels of students in science. To address such a problem, a supplemental learning resource in selected topics in Chemistry written in conversational Filipino was developed and validated for Senior High School non-science students. Two research designs were employed, namely, the Research and Development (R&D) design for the development and expert validation of the material, and a QuasiExperimental design for the end-user validation of the material. Since a modified validation tool was used, five science and education experts assessed the validation tool and rated it to be valid to a very great extent. Another set of five science and curriculum experts, using a reliability-tested modified validation tool, rated the learning material to be valid to a very great extent in terms of objectives, content, language use, instructional characteristics, acceptability, and usability. Non-randomly selected thirty-eight students from an intact class in a Senior High School in Tarlac City were split-halved into control and experimental groups and were administered the pre-test and post-test to establish the effectiveness of the learning material. Pre- and post-tests scores, along with their gain scores, were analyzed using a tTest. While results showed that there was still an increase in their performance regardless of the use of the supplemental material, it was also revealed that the administration of the supplemental material significantly increased students’ performance as compared to its non-supplementation. It is therefore recommended that the integration of local community language in learning materials should be considered as an effective way of contextualizing and deepening the understanding of students in science lessons.

Keywords: Conversational Filipino, Supplemental, Learning resource