1. Talk to the coach about your worries and tell him what you would like to do.
2. When that fails, have both your parents talk to the coach about their worries and tell him what they would like to do.
3. When that fails, have both your parents talk to the Athletic Director about their worries and tell him what they would like to do.
4. If that fails, have both your parents talk to the School Board about their worries and tell them what they would like to do.
5. If that fails, work with your private coach to train correctly in secret.
DO NOT QUIT YOUR HS TEAM.
I speak these things from years of experience working with good, flexible HS coaches and bad, egotistical HS coaches. Calmly go up the chain of command using your parents. Do this before the season starts. Do not give it 2-3 weeks to see how things are turning out. If the coach is a good coach, he will listen to you and work with you and your private coach.