My son is 15 and in 10th grade. What I found about high school is that the difficulties your child is having in middle school will also be the ones they will have in high school. One big difference is how aware my son is of the behavior of his classmates towards him. He previously had been pretty clueless when others made fun of him or mocked him.

My advice is to make sure the high school knows what the long term goal is and work toward that. If college is in the picture ensure all classes qualify. For my son is is not the actual curriculum he struggles with but rather the organization of his assignments, relating appropriately to his peers and understanding that expectations increase every year.

The School should have an IEP-(individualized Education Program)set up for her. Talking with the schools social worker or who ever heads their special education program should be able to get one set up an IEP meeting. You would be included in the meeting to help come up with the best education plans.

Maybe ask about the possibility of a one on one para/aide. Someone that could escort her to and from classes, even sit in classes and help her. I have seen this done in a few schools I've been to. It should be available in a large school, with setting/situations that can be over stimulating.
Oh also having them put a risk(concerns,dangers)/care (how to prevent and handle) plan into her IEP so her teachers/aides will know what to do

I wonder if you can visit some clubs there, or even swimming team that she might like to be involved with it. Then there might be some current h.s. students in her interest group that might agree to be like big brothers and sisters for her. Also maybe a para educator could assist to ease or smooth some of her social challenges. And the school staff can be asked to emphasize tolerance, acceptance, helpfulness, kindness. Through the Virtues Project there is an virtue vouchers activity where students catch one another in the act of doing a virtuous action and their name is noted on a paper brick and "virtues wall" is constructed! You can see if the counselor might help with this, or the student body officers.

Good luck - my son goes to Jr. High after next year and my daughter goes to high school next year - so this advice is for me too! (My daughter is not on the spectrum but it is still daunting!)

Also, you might want to check out SoundHealthOptions.com (near Athens, Ohio, developed by Sharry Edwards) for a practitioner near you. One girl was getting D's and with frequency "balancing" she got almost all A's! She was much more socially up with her peers as well!! There is a youtube video about this.

For a 14 year old, it might be more useful for her to talk to a counselor or therapist. Remember being 14? I thought my parents were pretty out if touch :) Sometimes it's just better to hear that kind of stuff from someone else - not a parent.