Not a big deal, he's off to the side by 10" - 12", he isn't being ostracized. If anything, they are treating him like a normal kid, by making him have to fit in with the group. I remember those class pictures, they were always rearranging the kids for speed and picture clarity.
It's a double edged sword. If you make too many special modifications to normal every day events like this, the kid's classmates look at them like some pitiful freak that needs all this special help. Also you can't really take him out of the chair and have him sit with the other kids(perhaps with some help from the teacher) because everyone's worried about being sued.