Tips on how to keep my stepdaughter more focused in school?

She (15 years old) has ADHD, but doesn't qualify for accommodations and she refuses to take meds. She'd have straight A's, if it weren't for her neglecting to turn in assignments or "forgetting". She's not motivated and I know her apathy (sleeping through class, playing chess online, solitaire, doodling, pretty much anything other than taking notes) towards school is probably exhausting for her teachers. She gets an A on every test she takes, but doesn't turn in assignments which leads to her getting B's, sometimes failing the whole semester until she turns in just enough assignments to pull it up to B. She seems to make it her mission to be completely average. I know she has an attitude problem towards her teachers, I feel bad for them. What can I do to make it easier for her teachers and keep her more focused?