Cathy, it's good to see you here, glad you made it!!
Kids that age dont seem to realise how important their grades are, you not alone on this, my son is the same "happy go lucky" school is, well just that. He has to sit down, and do school work for 1 1/2 hour each night for me now, hes grades dropped this first semester, so now i too am putting my foot down.
You are a good mom, she will appreciate you later on. This is not an easy age.