Being a minor yes it is ethical. See minors under 18 in the USA unless they have been court emansipated minors cannot decide their own mental and physical health decisions or enter into a legally binding contract.

Any changes in your mental or physical health treatment must go through, be approved, and decided by your parents until you reach your 18th birthday.

As for stopping therapy since you are legally a minor your parents can force you to remain in therapy either by taking you directly to the appointments, finding a treatment facility to place you in and or taking you to the local ER for involuntary commitment or going to court and having you court mandated into therapy and or court mandated into involluntary commitment.

My suggestion sit down and try talking to your parents instead of telling them "I don't want to go to therapy 2x a week and Im not going!" say mom what do you think of maybe cutting my therapy time back to once a week for a bit. I want to see how I would do on that type 0f schedule. I've learned so much so far (and go into detail about your better coping skills). Maybe with this approach your parents will see that you aren't just wanting to drop out you want whats best for you.

Hang in there