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

[Fire Storm]

Your daughter is acting like a 2 year old, trying to get her way. Explain to her that your are there to help her, when she wants your help. She is upset about being taken away from her friends. Tell her that it hurts you to see her hurting, but that she is only hurting herself by failing in school.
I lost my job this summer, and had to move my 15 and 16 year old out of state. My 16 year old was very excepting of this, but my 15 year old was very angry, and told me the same thing your daughter told you. I told him that as long as he failed school, he could not talk to his friends back home on the computer, or by phone, but as long as he keeps his grades up, he'll be able to talk to them on the computer, go home at Christmas and in the summer (If I can afford it, and help saves the money to help pay for the trip).
Also, most schools having psychologist, or some kind of counselor that they can talk to.
I put a password on the computer, so my son can only get on it, when his chores and homework are done. He understands that D's and F's on the report will get the computer taken away for 9 weeks, and he won't get to go home for Christmas.
I have also explained, that as his parent, it is my job to make the best decision I can for him and his brother, and I am sorry he is unhappy with those decisions, but in just a few short years, he will be 18 and old enough to move out, live where he wants and be responisible for himself, and make decisions regarding his life. Until then I am the parent and I get to make the decisions and rules. If possible, I try to let them have choices and help make important decisions. Unfortunately, our move to Texas, was one that had to be made without input form the kids....it was a matter of a job.