A Test to measure achievement in quantitative economics among secondary school students was developed and validated in this study. The test is made up 20 multiple choice test items constructed based on quantitative economics sub-skills. Six research questions guided the study. Preliminary validation was done by two experienced teachers in secondary school economics and one expert in test construction. The pilot testing was conducted to ensure compatibility of the test items while test try-out on 515 students yielded the data for item analysis. Analysis were attained through SPSS and Bilog MG using Item Response Theory (IRT) three-parameter logistic model (3PL) to establish item difficulty, item discrimination, and the guessing value. The empirical reliability of the test was 0.86. The test was found to be of good quality, valid and highly reliable. The test is ready and can now be used to assess students' achievement in quantitative economics in Nigeria and other countries.