My daughter is starting high school in a few weeks as well. We're going to start with the 504 and then apply for the special needs program which is much more powerful and will allow her to miss more days than the 90% required attendance and give her more flexibility. Most of her 8th grade teachers didn't even know what a 504 was. Because she has RND in her hands and can't write, we're getting her a lightweight ultrabook laptop to take notes with in class as much as she can.
I am concerned about the crowded hallways, getting bumped, walking to her locker (which we requested a central location) as well as just keeping up with all of the work and making enough classes to make it through, not to mention having a somewhat normal social life.