How should I react when my 15 year old daughter gets bad grades?

[Stareyes]

My 15 year old daughter just came to live with me. She lived with her father from age 10 to 15. He sent her to me so she could get more help with her schoolwork and attention in general. He works late and does not help her much with her school work.

I live in another state and she does not like living with me or the school that she is going to. She was throwing tantrums in the evening because of this and then saying she was going to "fail."

She did very poorly on a book report that she had to do and on Chemistry quizzes/ labs.

I don't know how much I should be helping her. I try to quiz her and review her reports. I don't want to rewrite them though.

I feel responsible for not living up to her or my ex-husband's expectations because I am not helping her to achieve A's and B's in school. She was not gettting good grades at her other school.

How should I handle her bad grades in this school? The grades should teach her about her tantrums and stop them.