I lie about my report card?

I'm a wreck, I generally get good grades, but I hate telling my parents bad grades, I just can't do it. My Mom and Dad get so freaking excited over it, they yell at me and say that I will be a loser and not amount to a sack of Sh*t. So I lie about my grades and now report card is coming and I know it's gonna be a long day..Can you guys give me advice, I mean this is the only thing I lie about. How can you tell your parents the truth and they never get mad at you? That would be impossibly. And what makes my situation worse, is that they compare me to my sister who gets straight As all the time. Please give me some good advice.