First, it doesn't mean that a teacher can teach any musical instrument. There are specialties in the technical field, and so are music teachers. They are proficient in one instrument, but the music is interoperable, and other similar instruments will be easy to use.

Second, not all levels can be taught. Most of the teachers in the musical instrument store are regular teachers in the Conservatory of Music or professionals who have worked in music. For example, some can teach 1-5, but not 6- 10.