In spite of the fact that career guidance in high schools has recently emphasized students' academic achievement, it is desirable that high school students develop career planning for future selection of their majors at the university and/or jobs, by considering not only academic achievement but also interests and attitudes. The primary purpose of this research was to investigate how high school students react facing their choice in future careers. For such purpose, we specified a causal model in which some relationships were assumed between eight constructs of career planning taking into account both aptitude and achievement. The model was subjected to covariance structure analysis, using data collected from 12,788 students in 84 high schools throughout Japan. It was shown that the appropriateness of the FIT Index was considerably high while some path coefficients were statistically significant, thus establishing the validity of the assumed model. From the analysis, it was found that guidance emphasizing academic achievement was not independent of the guidance emphasizing scholastic aptitude.