Competency in making inferences is an important aspect of student learning in the twenty-first century, for making better-informed decisions. The purpose of our study is to investigate the type of science capital that can predict the science inference competencies of lower track students. Science capital comprises diverse social capital, cultural capital, and mental schema. A total of 1,397 Normal Academic (NA) and 637 Normal Technical (NT) Grade 7 students from 37 public secondary schools in Singapore participated in the study. Three separate science inference tests were administered to the students over one academic year, and test scores were calibrated and equated using Rasch analysis. The relationship between students' perceptions of science capital and their development in science inference competencies was investigated using Ordinary Least Squares regression analysis. The results indicated that NA students' self-views in science learning and their views about the nature of science were significant predictors of their scientific inference competencies. For NT students, their views about science teachers was the only significant predictors of their performance on making scientific inferences. Based on the research design and findings, we draw implications for local and international science curriculum policy. Additionally, we demonstrate the usefulness of Rasch analysis.