I really worry that you will be trading one set of concerns for a much bigger one if you switch to the school you describe. An "alternative" school with low scores may not give your daughter the intellectual stimulation she needs. She may gain a false sense of feeling good about herself, because she is a top student, but may be bright enough to recognize that the kids she is comparing herself to are not doing well academically. It may be difficult for her to find friends.
I think some meds work well for some kids with ADD-Inattentive. You could give meds a try and see what she thinks. Otherwise, she may benefit from a "coach" or special instruction in ways to make herself focus and reduce the daydreaming. I am not sure that giving her easier work will make it more likely she will focus. She will still have to come up with the "right" answer.
High school does get easier. While in math you have to show your work to get partial credit (otherwise a wrong answer is just a wrong answer), there is probably less emphasis on methodolgy and more on understanding (multiply any way you like, do not have to use the lattice method for example). In Lang. Arts a student may have to follow steps: note cards, outline, rough draft, final draft, which some kids find excruciating. However, there may be more room for, and even encouragment of, divergent thinking.
The other thing you can do is get a special ed plan in place for your dd if she has an ADD diagnosis and gifted IQ scores. Perhaps she can be excused from certain busy work or allowed to work in her own way. Unfortunately, however, to some extent she will have to learn to work within the system both for school and eventually for most kinds of work.
Good luck
