This study collected data from 75 countries in 2018 from the World Bank’s statistical report, integrated mathematics and science learning achievement into a comprehensive index and ranking, and explored the relationship among the years of education, the enrollment rate, per capita income and learning achievement in 71 countries. The results were as follows: (1) Among the 75 countries, the five countries with the best academic performance are Singapore, Hong Kong, Estonia, Japan and Korea. (2) The years of education in all countries had a significant impact on per capital income, while the rate of higher education was not. (3) 71 countries’ years of education, rate of higher education, and per capita income had a positive effect on academic achievement respectively. (4) 71 countries’ per capita income had partially mediating effects between years of education and academic achievement, while the rate of higher education was not. The contribution of this research lied in the discovery that the country’s economic development was an important mediated factor between education investment and student learning achievement. In-depth discussion of conclusions and suggestions were made.