Back to school is a big moment for someone who has autism. For me, I always enjoyed school and learning and making friends. I do understand it can be hard though. Here's some things I had in my school years that you or your child can use.
My family had social stories for me to prepare what the school would be like and what to expect from the schedule. I also had an IEP and a regular meeting with a staff member to see how things are going. Accommodations are something I highly recommend as well. These accommodations can be things like a hall pass, extended time on tests, and copies of notes in case the time it takes to write down the notes isn't up to speed.
In addition, meeting with the teachers before school starts is something I did so I would know what the teachers are like. Letting them know about autism is a key point too. The only regret I had was not sharing this with a teacher I had who was a bit too strict for me that I was autistic. She was a bit hard on a lot of the students in general though. Other than that, letting the teachers know is a good way for an autistic student to get acquainted with the environment as well as develop a relationship with other students and staff.
Hope everyone has a good back to school!