I don't have anything specific to share, but I know from talking with other parents that you aren't the only one to go through this. Anxiety is hard.
You are on a solid track, checking out your bus schedules, etc. Next, why not see if you can find a good escape spot? A place to go when you feel you are nearing meltdown and need to self mitigate. And then write up a note for your teachers, to give them first day of class, that explains you have AS and may get overwhelmed, in which case you will leave the room suddenly to calm yourself down and don't want them to think you are being rude.
The school may be able to help you pick a safe spot, as well.
What I call an escape clause is a common IEP item for kids, and is a really useful tool at all ages, assuming you can recognize the build up that leads to meltdown well enough to take action.
What do you do for self-calming? My son paces, which he can do anywhere he can find space.
If you have an action plan, if should help ease the anxiety.
_________________
Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).