The purpose of this study was to investigate the effects of private tutoring expenditure on two types of Korean students' academic achievements as measured by standardized test achievement and by school performance achievement, applying 5-year data from Korean Educational Longitudinal Study (KELS). It was found that private tutoring expenditure consistently appeared to have statistically significant effects on standardized test achievement. On the other hand, private tutoring expenditure did not have statistically significant effects on school performance achievement. It can be stated that regarding standardized test achievement, some portion of Korean students' academic achievement could be a product of "shadow achievement."