A slow song will indicate a sad or emotional state of mind in a student. The importance of music may not be important at the time but it will be important when a student reaches a level a talent when they can learn to express themselves not only rough music but also as a person. Ideally music should be required in every school to try to make students understand what music is really about. Music is an expressive way for a student to get through to others and themselves. In the real world, that is virtually impossible.
All music educators can do is try their best in order for a student to achieve their maximum goal.
For some students music is just another class that their parents made them take, but to some students it is all they have. Some students are not talented in sports or any extracurricular activity but they have of gift of knowing how to play and understand music. Music can be competitive but on an individual basis and not necessarily on a team. I would love to see a rock medley played in a high school band, but that is not moral or it is against the school curriculum. Any kind of music is appropriate as long as that it is used in a way that a school board, a principal, or a teacher will not be embarrassed.