How can I deal with my depression and suicidal thoughts?

It all started about 2 years ago. I started getting grades below my parents expectation. Then last year I started getting C's. I tried harder and harder but I just can't understand the material. My parents are yelling at me constantly and are threatening to send me to another school or Asia even though I don't want to. I feel like I can't live up to their expectations of life. They always want me to be like my older sister who is an over achiever. I simply can't. Due to the way my parents talk to me, I feel like their lives would be a lot easier if I just ran away or killed myself. What can I do?