You are way off base. Obviously the girl's parents want her to have a better education than what she can get in the public school. They pay taxes and the school should allow her a spot in the band IF she makes the competitive cut.
It blows my mind that people like you begrudge someone who wants a better education the ability to join in on some extra-cirricular activities. Otherwise, its taxation without representation. As long as the kid is good enoug to make the team/band/, Big brother shouldn't be allowed to take your money and slam the door in your kid's face.
Are you suggesting that since my daughter goes to a private school and not a public school that she should be allowed to participate in extracurricular activities at the local public school because I pay school taxes?