Park et al.(2012) examined the impacts of coeducation in high school on the college scholastic ability test using random assignment in Seoul high schools. However, the student random assignment in Seoul within a school district was performed only within 30 min commutable areas using public transportation and Park et al.(2012) did not aware of this rule. This paper reexamines the question by matching nearest two single sex schools with a coeducation school within a school district. We found single sex school students achieve higher test score than that of coeducation school for both male and female. The magnitude of test score improvement for female is smaller than that of Park et al.(2012). However, the magnitude for male is bigger than that of Park et al.(2012).