It's okay. They can take the hate that you throw at them. They aren't here to be your friend. You have enough friends. However, you only get two parents. Their job is to love you, guide you and protect you.
My parents wouldn't let me date until I was 16 too. Did I hate them for it? You bet! Did it make ANY sense to me? Absolutely not. Did it ruin my life? No. It was a rule. The reason behind the rule was that they didn't want me to do something that they didn't think I was old enough to handle. Did I agree? NO! Were they right? I don't know. But I do know they had my best interest at heart. The point is, you are living in their house, under their roof and are expected to follow the rules that they give you. When you are 18 - or when you are living on your own - you are going to be able to do whatever you want. Honestly, it's really a short time when you are under their guidance. It stinks but you follow their rules as a sign of respect.
It sounds like you are pretty smart. Are they expecting A's because you are an "A" student? I'm betting that you are. I would think that if you were a "C" student, they would be unreasonable to expect to see all "A's." They want you to do your best...and your best sounds like "A's." If this is untrue, you may need to seek out the help of a teacher or guidance counselor to back up your claims that you are already doing your best and that for them to expect all A's is totally unreasonable.
As far as being embarrassed in front of your friends....that's one you'll just have to unfortunately live with. But know this....the kind of parent who wants to be their kid's best friend and the kind of parent who is permissive about things that are illegal, immoral or unethical....are not the kind that are going to take you far in life. Those parents are too wrapped up in their own lives and their own dreams to make the effort to teach and guide their children.
Believe me, your parents DO NOT enjoy being in conflict with you. It would be much easier for them to give in to you and let you do the things you want. They don't, though, because they would rather see you mad at them then watch you suffer from the consequences of a fateful decision.
Stay safe.