I could have written SO much more (and I will if you ask me to), but I think OP deseves some help already.
>>1 I have one main tip for you:
Don't become demanding of yourself.Even as your parents push your grades, remember that while grades can be important, grades don't measure personality or intelligence. Grades measure obedience, to put it bluntly. Grades measure whether you read what you were told to. The measure whether or not you did your homework like you were told to. Intelligence is something that includes so much more than just your math or writing skills - intelligence includes how cunning you are, how quick your mental reflexes are, how well you can comprehend topics, how well you handle yourself in difficult situations, et cetera. "Street-smart" is a bigger part of real intelligence than "book-smart" is, mainly because life (believe it or not) isn't actually about books.
Keep that in mind. Obviously, I still suggest you try to get good grades and keep your parents happy. Your parents do sound like good people, albeit a little up-tight. However, I don't know them, so I can't really say that. Keeping in mind that grades aren't your life will help; when you get a bad grade and they're mad at you, don't go, "I screwed up!" Instead, go, "Well, there's more to life than grades. Anyway, I'll just try better next time."
As for behavior, remember that you're a kid. You're not perfect. You're still learning. You still fuck up on half the shit you do. Why? Because that's what kids do. We don't know half as much about the world as we like to think. It's best to understand that (even if you don't admit it to an adult's face, keep it in your head).
Your "behavior" is part of:
1. The learning process of becoming an adult, and
2. Your personality.
If you're a fun, out-going person, don't let your parents change that. Be a bit more quiet around them. I mean, you should always keep yourself in check and make sure that you're not being too immature, but don't be afraid to be yourself because your parents told you not to.
If you're a quiet person, and they want you to be more out-going, fuck you parents. Quiet people are cool
o/
\o
(Don't be afraid to make friends, though. If you're afraid of people in addition to being quiet, you might want to start listening to them.)
/ahem
Anyway, yeah. That's how I handle the pressure I get. Unlike you, though, I get most of my pressure from myself. My mom's pretty laid back with grades and appearances, and my behavior is pretty good to her, so I have to keep myself in check. Arguements are ten times more annoying when it's yourself you're argueing with.
Just... don't become your worst critic. I'm warning you now. Unless you're going to art school, never let yourself be your worst critic. Criticize yourself without breaking yourself >>'
Got off topic. ANYWAY, I think you get my point.