Hi L.! Boy, do I understand what you're going through. My son Kyle started high school this yare, and he too is in danger of failing because of not turning in work. Same problem in middle school. What I have done this year, is I have written a contract with what I expect from him form school. For me, I wrote that he must turn in every single homework, classwork, and extra credit assignment. I catorogized it into 2 weeks. I listed privilidges he will get if he does this (and he will get them all at once after the initial 2 weeks). Things like, cell phone, paid for babysitting his younger siblings, computer time, etc. But, the agreement is if he misses even one assignment.....the 2 weeks starts over with him getting none of them. The minute he makes it to 2 weeks, he gets all on the list. I made him sign it. I signed saying I would provide him with things like an adequate place to do his work (quiet, no TV or radio), and will get him extra help if I cannot help him. I know that for my son, taking away one or 2 privilidges just doesnt make a difference, because hes got other things. But, by allowing him to have ALL the privilidges the minute he reaches his goal, that seems to be a good modivator for him. And he has to get a progress report filled out by every teacher Tuesday and Friday. And if he misses one teacher or one section on the form, starts over. So far this is appears to be starting to work. I think there is something about the fact that if hes sees it all written down, he is realizing just how much he is missing out on.
Sorry for the long winded response, but I know that that this is the most frustrating thing for me from a parental standpoint! I hope things get better with your daughter!