Representation of ability/disability on screen

Auggie is represented as dum. The other school children tell him that science is very hard and even ask him if he knows what an eraser is. This could make the other children look mean but really they don't know his situation.
Near the end of the clip we actually find pout that he is actually quite smart. This is because he has been home-schooled, which removes the distractions from normal school like friends and other students. They then continue to ask whether hes been part of a car crash or whether he was caught in a fire. They ask this because of how his face looks. They might do this because he acts normally and is quite smart but looks different to everyone else.
Because he looks different the children think he will be mentally disabled and not understand the things they learn and talk about at school. The fact hes been home-schooled, to the other children, means he he hasn't been educated and he doesn't really know anything. He actually corrects the other child, who was picking on him, how to say the word properly and then moves onto say maybe he could be home-schooled as well.