Higher-level mathematics courses in upper secondary school serve as a critical filter to future educational courses and careers in Science, Technology, Engineering and Mathematics (STEM). However, the percentage of senior school students in Australia undertaking higher-level mathematics courses is decreasing. Given that these courses provide students with skills and knowledge integral to STEM disciplines, it is important to discover factors that serve to encourage or detract students in choosing higher-level mathematics courses. Considering that educational and career choices are influenced by personal interests, values, and expectations, the purpose of this study was to design and validate a bipolar format survey instrument to investigate motivational factors on mathematics course choices of Year 10 Australian school students based upon Situated Expectancy-Value Theory (SEVT). A 25-item survey instrument using a bipolar format was developed to measure: Expectancy for success (operationalized as Competence-beliefs); Intrinsic value; Attainment value; Utility value; and Cost in relation to mathematics. Confirmatory and exploratory factor analyses of data collected from Year 10 students (n = 886) revealed a four-factor model consisting of well-defined factors of Competence-beliefs, Intrinsic value, Attainment value, and Utility value. Unexpectedly, the items designed to measure the Cost factor dispersed variously into the factors of Competence-beliefs, Intrinsic value, and Utility value, and conceptually plausible explanations are offered for this finding. This survey represents a promising instrument for measuring predictors of mathematics course choices in senior school students. The study findings also suggest interrelationships between specific cost dimensions and other factors relevant to the measurement of SEVT constructs more generally.