Honest? I would get his input and see what he thinks would work for him. If he is really stressed about it write a few options down and try one at a time until he finds what works for him. Does he have a case manager? Does that person know AS pretty well? Let your son know that is his safe person on campus and he can go to them if he is having trouble and if he can't do that perhaps he has a cell he can text you mid day for possible problem solutions.
My 16 yo never even used her locker. She just could NOT manage the combination and all that stuff so she kept her stuff in her cubby in the band room and eventually worked out her own routine. At that age whatever I suggested was wrong anyway (LOL).
My 2nd ASD kid is going into high school this year as well. He has a specialized program so hopefully that will help but I KNOW there will be bumps in the road and I will deal with them when they arise.
Some things that have helped:
1) Getting the schedule a head of time as well as a map and learning the routes around the school as well as where all the classes are. Walk the route when the school is empty. Also learning where the bathroom is, the nurse, the office and meeting their special ed teachers/case manager.
2) Some method of contacting me when surprises arrive. A cell phone has been a life line for them when they are lost and confused they send me a text. Not supposed to text at school but ALL the kids do it honestly. If it is an issue I will talk to the powers that be as to why my kids were texting me.
3) Being involved in some sort of activity at high school that preferrably starts even before the year. Both kids are in marching band. With band camp, band practices, etc during the summer both kids already knew classmates and were well familiar with the school before starting a single class. Also getting them involved in something like that helps with the whole social factor.
Good luck! At least I can say in some ways high school has been better than middle, in other ways I am getting gray very very fast.
I agree with Rene that I would talk with him about it.