The study evaluated the academic achievement of Senior Secondary School students on a Standardized Economics Achievement Test in Bauchi State, Nigeria, using an ex-post facto research design. The population comprised 18,389 Senior Secondary students. A sample of 377 students from eight schools across three educational zones was selected using cluster sampling and Krejcie and Morgan's sample size table. Data were collected using the Standardized Economics Achievement Test (SEAT), with validity and reliability established through Kendall's coefficient of concordance and KR20. Difficulty and discrimination indices for item selection were found to be 0.40-0.63 and 0.3-0.5, respectively. Raw scores were converted to standard scores using Z-scores and T-scores.

The study posed seven objectives, research questions, and four hypotheses. Descriptive statistics (mean and standard deviation) were used for research questions 4-7, while t-tests were employed to test all hypotheses at a 0.05 significance level. Key findings included:

- Significant differences were found in the mean achievement of students in rural single-sex schools compared to their coeducational counterparts, with rural single-sex students performing better (t = 5.598, p = 0.00).

- Urban single-gender school students also achieved significantly higher mean scores compared to their coeducational peers (t = 7.998, p = 0.00).

- No significant difference was found between the achievements of coeducational students in rural versus urban schools (t = 2.53, p = 0.800).

- Urban single-sex schools outperformed rural single-sex schools, with urban students showing significantly higher achievement (t = 2.708, p = 0.007).

Based on these findings, the study recommends that the government consider establishing more single-sex schools and single-gender classes in both rural and urban areas. The results indicated that students in single-sex schools, whether rural or urban, achieved higher scores than their coeducational peers, suggesting a potential benefit to single-sex education in improving academic performance.