The present study was designed (1) to classify high school students according to the weighted scores of a 25 aptitude test battery and their achievements on the seven subjects, by the method of principal component analysis, and (2) to investigate whether or not high and low achievers could be discriminated on the basis of the linear discriminant function of 10 aptitude test scores in this battery. Twenty hundred and three high school students of technology answered the items of the aptitude test battefy which consisted of following subtests : (1) general and vocational aptitude test (10 scales), (2) interest test (8 scales), (3) extroversion v. s. introversion test (6 scales), (4) work aptitude test (1 scale). In addition to these items, their achievement records on the following seven subjects were included : Japanese Language, Foreign Language, Social Science, Natural Science. Mathematics, Professional Course. Drafting. In the first part of the study, the principal component analysis was applied to these data (32 variables about 203 S's, in total). As a result, six main components were extracted which represented about 60% of the total variation of the original data. The meanings of the first three were scientific thinking, general aptitude, and scientific v. s. literary interest, respectively. Based upon each of these component scores, classification and total evaluation of the individual student were established. In the second part of the study, ten aptitude variables (verbal and mathematical ability,scientific v. s. literary interest, work aptitude, and six extro-version v. s. introversion scales) were chosen as predicton from the original item pool which seemed to have positive relations with the seven achievement variables as a result of the principal component analysis, and 203 S's viere grouped into the upper and lower achiever classes based upori their ratings of each seven achievement variable.