Here's my question: As parents and other associated with GT, do you agree with the school's decision? If so, why do you agree?

Just on the face of things I would say no that I do not agree. It seems that your daughter passed the class and has likely mastered the material. I think that she would be bored repeating it again. Do you have achievement test scores in math or something similar to point to that would establish the fact that she excels in math. Also a letter from her former pre-algebra math teacher at her old school stating that based on her observations of having your daughter in class there would be no benefit to her repeating that class over again might help. You might also want to gather some information together about the general benefits of accelerating a gifted child. The school would not hold back a child that got an 81% in math and essentially that is what they are doing with your child. Again, I think I would just try to gather as much "proof" as you can that your daughter is ready to move on and try to convince them that the grade itself is not the whole story. There must have been a reason that your daughter was accelerated in the first place and I would start there and move forward. Good luck!