Since you say you're running out of options on trying to help your daughter improve her grades, that means you've tried several approaches. Not knowing what you've tried unsuccessfully, I can only suggest things to consider that you may have already tried.
The only way to know if it's related to bipolar disorder is to do a complete medical review. Consider not just bipolar but normal teenage body and hormonal changes. For example, a lot of teenagers have trouble falling asleep early or easily, so they stay up later and sleep less.
Could it be teenage-related? Sure, in many ways that you & I might not even think of. A friend may have deserted her. There could be a new friend (or group) who are influencing her negatively. There could be a clique that's giving your daughter a cold shoulder or circulating nasty rumors about her. She might be having problems with Facebook activities. There might be sexual harassment or bullying that you don't know about. She may be romanticizing over a guy at school who may be playing her along or may be oblivious to her existence. She may feeling pressured by the advances of a boyfriend, or she may have done something she regrets. She may have a huge crush on a teacher. She may be spending hours and hours writing out baby names instead of thinking about math or social studies. She might be questioning her sexual orientation. She might be doing drugs. She may be fretting over her appearance (clothes, make-up, weight, shape, etc.) so much that her mental energy is going into personal and social issues as top priority, with schoolwork taking a backseat (in and out of class). She may be living in a fantasy world, weaving endless dreams and not attending to academics. Anything is possible, but chances are that whatever is on her mind is fairly harmless in the larger scheme of things.
She could be worried about you or your spouse, the economy, the state of the world, or whether she believes in God.
The problem may be just academics, with Increasing demands that are overwhelming her.
Have you talked with all her teachers to find out what the problem areas are? Is she completing all homework and turning it in on time? Does she bomb tests? What do teachers say about her academics & behavior?
I'm sure you've talked to your daughter without gaining insight. I would probably talk to her counselor and ask the counselor to call your daughter in for a chat — with no mention of having talked to parents — and just chatting about how things are going, getting ready for next year (high school?), and bringing up the lowered grades.
If, in the next few weeks, you don't get any answers that explain the decline in grades and suggest solutions, I'd ask for an evaluation for special education services. It may feel like a bit of a fishing expedition. When I asked for my daughter to be evaluated in middle school, I thought maybe, just maybe (but not likely), she had ADD inattentive type that we hadn't noticed before, and if so, then maybe she'd be eligible for a 504 plan. In the meantime, I continued harassing her to get her work done, continued offering bribes & awarding punishment, all to no avail. A couple of months later, with the evaluation complete, I discovered she had an anxiety disorder and qualified for an IEP. You could have knocked me over with a feather! Things began to make sense. I always feel sad when I look back at how I blamed my daughter for her problems.
Daunna Minnich
Moderator, JBRF Education Forum