They have schools that are for kids with Autism. I know an older kid in Arizona who goes to an autistic school
Also, if your child was evaluated through the school system already... your child will get an iep. My daughter went to a public school for vpk and up... and she had an iep with the resources (like speach/aba/food therapy) to help her. By the second grade, my daughter didn't need as much help, so she transferred to a different school with a more "normal" class setting. I hope your son has a great first day of school! I literally sat in the parking lot the first day of school, and stayed until school was over lol. My daughters teacher communicated with the parents through an app, so o got sent pictures and updates about my child during the school day. I literally made an album of all the pictures that the teacher sent while my daughter was in class. I loved that!
I was the same way when my daughter started school for the first time... she was only 3 though. I cried, and it stressed me out. My daughter was not doing well at this school. At the time, i didn't know she was autistic. With the school directors help, i got her evaluated, and into the school that has resources to help her. When my daughter switched schools to better fit her needs, she thrived! She spoke her first sentence within the first week of being at that school. I was nervous that my daughter was totally non verbal and starting school, but that quickly changed. I'm so thankful to the teachers, and specialists at the school. The teachers communicate with parents, and make it easy to reach them during school hours. I felt more relaxed. If you're nervous about anything, just express this to the teachers.