Lets take your proposed scenario for example, a kid is...
Art and Music programs should be mandatory for students in Grade School
Your argument is that students who aren't forced to take Music and Arts, will not get the chance to possibly discover a hidden talent for the arts. If a student doesn't want to learn The Arts, who are we to force them to? Lets take your proposed scenario for example, a kid is forced to play the piano at school, and in doing so, discovers he has an incredible talent for it. Just because you have a talent for something, doesn't mean you have to like it, and it doesn't mean you should be forced against your will to do it. If a student doesn't wish to learn Music, it probably won't matter how talented he discovers that he is, he still won't like doing it. That's why my proposal is for Music and Art programs to be optional. This way, students who want to learn how to play musical instruments and to paint, will be given the opportunity to do so, and students who don't want to, won't be forced to waste countless hours.