I've not much advice for you but I would contact the special needs section of this site.
Also contact the Aspergers society for some advice.
Fwiw most of my dcs classes have someone with AS in them.
If the boy is badly affected and his behaviour is very pronounced you may find that other parents complain a lot about him, and it may well be at he's not able to cope with a large group.
I know from my own experience, that having paid over a thousand pounds for tuition, I was really pissed off that there was such a boy in my Dds drama class. He was very disruptive of the class, as he screamed and flapped and ran around and fled out of the room, nonstop for the hour, and he also hid under furniture screaming every week, and had to be cajoled, and have one on one attention paid to him. The other kids didn't have any tuition or attention paid to them while he was like this.
His mother was very lovely, and the teacher was very lovely, and all the kids were very accepting and were very lovely, but the numbers dropped off in the class, as it was too stressful for the other children to have someone so stressed and unable to cope in their midst, and they weren't learning anything other than what this little boy needed.
You may need more help in the class, if his behaviour is very affected.