This study analyzed TIMSS 2003 data to investigate factors contributing to Singaporean students outperforming Malaysian students in mathematics. It found Singaporean students scored significantly higher overall and in all content areas. Singapore had advantages in resources like computer ownership. Characteristics like gender, parents' education, resources and attitudes significantly impacted achievement in both countries. Teacher characteristics mattered more for Malaysian students. The differences were largely due to Singapore's greater socioeconomic homogeneity and better implementation of strategies, rather than differences in characteristics between the countries.