The goal of this study is to help educate students by investigating how teachers perceive students` music aptitude. For this, the following tasks are executed: (1) To compute the correlation between students` music aptitude measured based on teachers` own criteria and music aptitude measured by IMMA, a standardized test; (2) To analyse the characteristics and criteria of teachers` measurement of students` music aptitude; The relationship between the teachers` measurements of music aptitude and the IMMA scores were .43(tonal) and .37(rhythm). There was a great difference between the two measurements. The teachers have a tendency to consider girls better than boys. They also have a tendency to confuse academic achievement, attitude, and characters with music aptitude. The teachers subjective judgement of students` music aptitude can be a problem. They need to use standardized music aptitude test rather than relying on their subjective judgements.