Hello and thank you for using Just Answer. I am sorry to hear about the problems that you are experiencing with your daughter. Her change in academic progress from middle school to high school is completely normal and experienced by many teen-agers both male and female. Grades and studying are simply not important. The social scene is what matters to her now more than anything. You are definitely not in the wrong by enforcing the consequences that you have already mandated. She does need the math tutor whether she likes it or not. Does she have a great deal of extra time? If so, how is it being utilized? Because of her poor grades, you must dictate how that time should be utilized for her. When she is at home, have her give the cell phone to you. If she is not doing research on the computer, do not allow her to use it. Limit her time with friends. She should be just going to school and then back home. She almost needs to feel like she is in jail. She should be spending her time studying and trying to earn back her cell phone usage, spending time with friends, going on the computer etc. When she starts putting forth the effort in her schooling and you see a change in her grades, REALLY praise her. On the other hand, maybe there are some deeper rooted problems that she is not willing to discuss with you. You can just casually ask her if anything is bothering her. Maybe she feels the pressures of teen-age drug and alcohol usage or having sex and does not know which way to turn but still wants to fit in with the "right" crowd. There would be nothing wrong with having her speak to a counselor or psychologist so that she can express her feelings to a neutral source. Even if you attend church, there are counselors who can assist your daughter. What might help or shed some light on the situation is that if you ask your daughter to write a letter to you about how she feels about her life: school, family, friends, future, etc. She may express some things in the letter that you are not aware of.
Hope this helps. If you need more advice, just ask. Have a great day!!!