@boomerang,
But it's the teacher who is going to have him all day. I don't know that involving the principal right now will be effective. maybe that's because my last principal was just plain ineffective. It sounds like you'll want him to have regular visits with the school psych...? If you want things in his class room to be in a certain way, give his teacher a copy. If you want him to have access to the school psych, have a copy sent to him or her.
Most kids get the help they need without parental help. Some kids get more help than they need with parental help. Some kids get best service with parental help. But, most kids don't start the school year with best service. Every new year/teacher involves a new learning curve.
Boomer, I still don't know what you want of the school. I would add more detail about what you're hoping to achieve. Do you want him to see specific specialists like the OT, the Psych, the sped department? Do you want him to have a privacy space inside the classroom to disengage in? Do you want him front and center where he can feel close to the teacher?