Abstract
This study explored the effectiveness of learning mathematics according to the STEM approach in developing mathematical proficiency with its five components (conceptual understanding, procedural fluency, strategic competence, adaptive reasoning, and productive disposition) in some mathematical concepts among second graders of intermediate school. The quasi-experimental method with the experimental and control group design was used. The participants were 40 second graders of the intermediate school in the second semester of the school year 2021-22. The experimental group (N = 20) was taught according to the STEM approach, while the control group (N = 20) was taught according to the conventional approach. Data were collected by a researcher-developed mathematical proficiency test measuring conceptual understanding, procedural fluency, strategic competence, adaptive reasoning, and productive disposition. Results of the t-test revealed significant differences in mathematical proficiency between the post-test mean scores for the experimental and control groups in favor of the experimental group. Implications drawn from the results are offered.