I wouldn't give up yet. One of my kids wanted to quit school and make money so she could travel. Didn't care what I said. Five years later, when she walked with diploma in hand, she thanked me for not letting her quit. What worked with her? Bribery. I paid her for A's. Some will scoff, but she has a fancy university degree and a wonderful career because of it. Maybe worth a try; the new Iphone is coming out soon; should be worth 1 1/2 hours of practice per week. Make it back on varsity should get her drivers training covered; remind her driving is not a right. Lol, I feel your pain Doug. Just tossing some ideas out. My #1 only responded to "my way or the highway", but that's a little extreme for sports.
As an economist would tell you..... The basic postulate of economics is that people respond to incentives. I'm a firm believer in providing incentives. I'm also a firm believer in bearing the costs of your actions/decisions.