The study Standardized Economics Achievement Test for senior secondary school students in Nigeria. Three research questions guided the study. The standardized test in Economics was first constructed by an expert as a valid and reliable instrument. The test was then used for standardization in this study. That is, ensuring that the Economics achievement test is standardized. It was administered to 3,000 students using the same guidelines with no case of malpractice. The sex, location and school-type norm of students were considered for standardization. The measurement of students in form of Percentile rank, Z-score, T-score and Stanine statistics were used as derived scores to normalize the students' raw scores, using the knowledge of the normal curve as the theoretical base. This completed the process that made the test a Standardized Economics Achievement Test. The result shows that the test scores were normally distributed through the use of Percentile rank, Z-score, T-score and Stanine. Recommendations were made that the standardized test could be used to asses and compare the measurement of students from year to year.