It would depend upon what music is being played; what lyrics there are. Rulings on music among scholars are diverse. Ayatollah Sistani says that it is not permissible to listen to music that is used for frivolous entertainment or sexual provocation, meaning that music that is NOT used for frivolous entertainment or sexual provocation may be listened to; for example, music that is composed to praise God. Interestingly, even the same ruling exists in Buddhism. You should have a discussion with the teacher to ask what kind of music they intend to teach, as unfortunately nowadays children are exposed to many indecent and adult-level sounds and images, even at school.