The 2015 revised high school curriculum has been designed to support students’ selection of subjects considering the student's career path, and the mathematics department also organized general/ career elective courses. This study was conducted to derive implications for ensuring students' choice of subjects ahead of the implementation of the high school credit system. First of all, focusing on subject options, I looked at the changes in Korean curriculum, composition of foreign mathematics subjects, and college entrance subjects, and the current status of ‘selective- oriented curriculum' in 1,709 general high schools nationwide and status of co-curriculum operation by education board of city or province. Several implications have been derived based on the findings. It was suggested that elective subjects and career tracks should be prepared so that students can choose their courses according to their career path, and that universities should designate essential subjects so that students can learn what they need and go to college. In addition, it was proposed that improvements in the system to prevent grades from being disadvantaged by the selection of mathematics subjects, and improvements in the completion path and subject composition should be made.