The dad you are offers empathy and compassion, the two most important parenting traits. YOU are the dad she needs. It can be tough when the parent also has ADHD, but you also bring valuable insights and experiences to the table:
Now, I am concerned about the lack of communication from teachers/school. When a student’s grades slip like that, or are incredibly low, teachers should notify parents. I’ve had the same struggle for several years. Now, in high school, SPED staff tells him that C’s are average and good, and tell me that he’s passing his classes when it’s time for report cards, so all is well. Grrrr! Makes me crazy! Most schools have a policy/approach to do as little as they can possibly get away with when it comes to special needs students.
I would make a formal request that you are notified when her grades drop below a C. If she has a 504 plan or IEP, ask that this accommodation be added. If not, it may be time to pursue more formal support in the school:
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism